[PowerPC] power9 f128 ABI issue: bitcasts can reverse halves #92246
Labels
Comments
Flipped endianess would be |
|
Yeah, more like maintaining scalar endianness but laying out a composite |
tgross35
changed the title
|
@llvm/issue-subscribers-backend-powerpc Author: Trevor Gross (tgross35)
Doing a roundtrip i128 -> f128 -> i128 should work but it appears to be broken when the calls are external, possibly depending on some optimizations. It seems like the `f128`/`i128` is getting split into two 64-bit values, which are getting reversed at some point.
Originally identified with rust in rust-lang/rust#125102. Source files: // transmute_lib.rs
#![feature(f128)]
#![allow(improper_ctypes_definitions)] // ok since llvm 18
use std::mem::transmute;
#[no_mangle]
pub extern "C" fn entry(a: u128) -> f128 {
unsafe { transmute::<u128, f128>(a) }
}// transmute_call_lib.rs
#![feature(f128)]
#![allow(improper_ctypes)] // ok since llvm 18
extern crate transmute_lib;
use std::mem::transmute;
use std::process::exit;
extern "C" {
fn entry(a: u128) -> f128;
}
fn main() {
let a = unsafe { entry(0x1) }; // bitcast in an external function
let res = unsafe { transmute::<f128, u128>(a) }; // bitcast back
if res == 0x1 {
exit(0); // correct
} else if res == 0x1 << 64 {
exit(1); // incorrect value with endianness flipped
} else {
exit(2); // unexpected value
}
}Versions: Compilation: Execution: The above should output 0. Full IR: <details> ; ModuleID = 'transmute_lib.1e179323af95c5c5-cgu.0'
source_filename = "transmute_lib.1e179323af95c5c5-cgu.0"
target datalayout = "E-m:e-Fi64-i64:64-n32:64-S128-v256:256:256-v512:512:512"
target triple = "powerpc64-unknown-linux-gnu"
; Function Attrs: uwtable
define fp128 @<!-- -->entry(i128 %a) unnamed_addr #<!-- -->0 {
start:
%_0 = bitcast i128 %a to fp128
ret fp128 %_0
}
attributes #<!-- -->0 = { uwtable "probe-stack"="inline-asm" "target-cpu"="pwr9" }
!llvm.module.flags = !{!0}
!llvm.ident = !{!1}
!0 = !{i32 8, !"PIC Level", i32 2}
!1 = !{!"rustc version 1.80.0-nightly (9c9b56879 2024-05-05)"}</details> <details> The only relevant part is in ; ModuleID = 'transmute_call_lib.1791869a4d73965-cgu.0'
source_filename = "transmute_call_lib.1791869a4d73965-cgu.0"
target datalayout = "E-m:e-Fi64-i64:64-n32:64-S128-v256:256:256-v512:512:512"
target triple = "powerpc64-unknown-linux-gnu"
@<!-- -->vtable.0 = private unnamed_addr constant <{ ptr, [16 x i8], ptr, ptr, ptr }> <{ ptr @"_ZN4core3ptr85drop_in_place$LT$std..rt..lan
; std::sys_common::backtrace::__rust_begin_short_backtrace
; Function Attrs: noinline uwtable
define internal void @<!-- -->_ZN3std10sys_common9backtrace28__rust_begin_short_backtrace17hf94855fdbb5829c5E(ptr %f) unnamed_addr #<!-- -->0 {
start:
; call core::ops::function::FnOnce::call_once
call void @<!-- -->_ZN4core3ops8function6FnOnce9call_once17h3056e9bd87d66482E(ptr %f)
call void asm sideeffect "", "~{memory}"(), !srcloc !3
ret void
}
; std::rt::lang_start
; Function Attrs: uwtable
define hidden i64 @<!-- -->_ZN3std2rt10lang_start17hdc6989dbc5702db1E(ptr %main, i64 %argc, ptr %argv, i8 %sigpipe) unnamed_addr #<!-- -->1 {
start:
%_8 = alloca [8 x i8], align 8
%_5 = alloca [8 x i8], align 8
store ptr %main, ptr %_8, align 8
; call std::rt::lang_start_internal
%0 = call i64 @<!-- -->_ZN3std2rt19lang_start_internal17he440c14c55fd4760E(ptr align 1 %_8, ptr align 8 @<!-- -->vtable.0, i64 %argc, ptr %argv,
store i64 %0, ptr %_5, align 8
%v = load i64, ptr %_5, align 8
ret i64 %v
}
; std::rt::lang_start::{{closure}}
; Function Attrs: inlinehint uwtable
define internal i32 @"_ZN3std2rt10lang_start28_$u7b$$u7b$closure$u7d$$u7d$17hdb386b686ec8565dE"(ptr align 8 %_1) unnamed_addr #<!-- -->2 {
start:
%self = alloca [1 x i8], align 1
%_4 = load ptr, ptr %_1, align 8
; call std::sys_common::backtrace::__rust_begin_short_backtrace
call void @<!-- -->_ZN3std10sys_common9backtrace28__rust_begin_short_backtrace17hf94855fdbb5829c5E(ptr %_4)
; call <() as std::process::Termination>::report
%0 = call i8 @"_ZN54_$LT$$LP$$RP$$u20$as$u20$std..process..Termination$GT$6report17h3606faab680ab85fE"()
store i8 %0, ptr %self, align 1
%_6 = load i8, ptr %self, align 1
%_0 = zext i8 %_6 to i32
ret i32 %_0
}
; core::ops::function::FnOnce::call_once{{vtable.shim}}
; Function Attrs: inlinehint uwtable
define internal i32 @"_ZN4core3ops8function6FnOnce40call_once$u7b$$u7b$vtable.shim$u7d$$u7d$17h956497c27ef6ef7fE"(ptr %_1) unnamed
start:
%_2 = alloca [0 x i8], align 1
%0 = load ptr, ptr %_1, align 8
; call core::ops::function::FnOnce::call_once
%_0 = call i32 @<!-- -->_ZN4core3ops8function6FnOnce9call_once17h9737a54d47c05e22E(ptr %0)
ret i32 %_0
}
; core::ops::function::FnOnce::call_once
; Function Attrs: inlinehint uwtable
define internal void @<!-- -->_ZN4core3ops8function6FnOnce9call_once17h3056e9bd87d66482E(ptr %_1) unnamed_addr #<!-- -->2 {
start:
%_2 = alloca [0 x i8], align 1
call void %_1()
ret void
}
; core::ops::function::FnOnce::call_once
; Function Attrs: inlinehint uwtable
define internal i32 @<!-- -->_ZN4core3ops8function6FnOnce9call_once17h9737a54d47c05e22E(ptr %0) unnamed_addr #<!-- -->2 personality ptr @<!-- -->rust_eh_p
start:
%1 = alloca [16 x i8], align 8
%_2 = alloca [0 x i8], align 1
%_1 = alloca [8 x i8], align 8
store ptr %0, ptr %_1, align 8
; invoke std::rt::lang_start::{{closure}}
%_0 = invoke i32 @"_ZN3std2rt10lang_start28_$u7b$$u7b$closure$u7d$$u7d$17hdb386b686ec8565dE"(ptr align 8 %_1)
to label %bb1 unwind label %cleanup
bb3: ; preds = %cleanup
%2 = load ptr, ptr %1, align 8
%3 = getelementptr inbounds i8, ptr %1, i64 8
%4 = load i32, ptr %3, align 8
%5 = insertvalue { ptr, i32 } poison, ptr %2, 0
%6 = insertvalue { ptr, i32 } %5, i32 %4, 1
resume { ptr, i32 } %6
cleanup: ; preds = %start
%7 = landingpad { ptr, i32 }
cleanup
%8 = extractvalue { ptr, i32 } %7, 0
%9 = extractvalue { ptr, i32 } %7, 1
store ptr %8, ptr %1, align 8
%10 = getelementptr inbounds i8, ptr %1, i64 8
store i32 %9, ptr %10, align 8
br label %bb3
bb1: ; preds = %start
ret i32 %_0
}
; core::ptr::drop_in_place<std::rt::lang_start<()>::{{closure}}>
; Function Attrs: inlinehint uwtable
define internal void @"_ZN4core3ptr85drop_in_place$LT$std..rt..lang_start$LT$$LP$$RP$$GT$..$u7b$$u7b$closure$u7d$$u7d$$GT$17h64db6
start:
ret void
}
; <() as std::process::Termination>::report
; Function Attrs: inlinehint uwtable
define internal i8 @"_ZN54_$LT$$LP$$RP$$u20$as$u20$std..process..Termination$GT$6report17h3606faab680ab85fE"() unnamed_addr #<!-- -->2 {
start:
ret i8 0
}
; transmute_call_lib::main
; Function Attrs: uwtable
define internal void @<!-- -->_ZN18transmute_call_lib4main17hfa19d9d60e61b95dE() unnamed_addr #<!-- -->1 {
start:
%a = call fp128 @<!-- -->entry(i128 1)
%res = bitcast fp128 %a to i128
%0 = icmp eq i128 %res, 1
br i1 %0, label %bb2, label %bb3
bb2: ; preds = %start
; call std::process::exit
call void @<!-- -->_ZN3std7process4exit17hb2f96155fda111fdE(i32 0) #<!-- -->5
unreachable
bb3: ; preds = %start
%_4 = icmp eq i128 %res, 18446744073709551616
br i1 %_4, label %bb5, label %bb6
bb6: ; preds = %bb3
; call std::process::exit
call void @<!-- -->_ZN3std7process4exit17hb2f96155fda111fdE(i32 2) #<!-- -->5
unreachable
bb5: ; preds = %bb3
; call std::process::exit
call void @<!-- -->_ZN3std7process4exit17hb2f96155fda111fdE(i32 1) #<!-- -->5
unreachable
}
; std::rt::lang_start_internal
; Function Attrs: uwtable
declare i64 @<!-- -->_ZN3std2rt19lang_start_internal17he440c14c55fd4760E(ptr align 1, ptr align 8, i64, ptr, i8) unnamed_addr #<!-- -->1
; Function Attrs: uwtable
declare zeroext i32 @<!-- -->rust_eh_personality(i32 signext, i32 zeroext, i64, ptr, ptr) unnamed_addr #<!-- -->1
; Function Attrs: uwtable
declare fp128 @<!-- -->entry(i128) unnamed_addr #<!-- -->1
; std::process::exit
; Function Attrs: noreturn uwtable
declare void @<!-- -->_ZN3std7process4exit17hb2f96155fda111fdE(i32) unnamed_addr #<!-- -->3
define i32 @<!-- -->main(i32 %0, ptr %1) unnamed_addr #<!-- -->4 {
top:
%2 = sext i32 %0 to i64
; call std::rt::lang_start
%3 = call i64 @<!-- -->_ZN3std2rt10lang_start17hdc6989dbc5702db1E(ptr @<!-- -->_ZN18transmute_call_lib4main17hfa19d9d60e61b95dE, i64 %2, ptr %1, i8 0)
%4 = trunc i64 %3 to i32
ret i32 %4
}
attributes #<!-- -->0 = { noinline uwtable "probe-stack"="inline-asm" "target-cpu"="pwr9" }
attributes #<!-- -->1 = { uwtable "probe-stack"="inline-asm" "target-cpu"="pwr9" }
attributes #<!-- -->2 = { inlinehint uwtable "probe-stack"="inline-asm" "target-cpu"="pwr9" }
attributes #<!-- -->3 = { noreturn uwtable "probe-stack"="inline-asm" "target-cpu"="pwr9" }
attributes #<!-- -->4 = { "target-cpu"="pwr9" }
attributes #<!-- -->5 = { noreturn }
!llvm.module.flags = !{!0, !1}
!llvm.ident = !{!2}
!0 = !{i32 8, !"PIC Level", i32 2}
!1 = !{i32 7, !"PIE Level", i32 2}
!2 = !{!"rustc version 1.80.0-nightly (9c9b56879 2024-05-05)"}
!3 = !{i32 1628919}</details> |
|
Looking at the generated assembly (compiler explorer): entry:
mtvsrdd 34, 4, 3
blr
main:
# <prelude omitted>
li 3, 0
li 4, 1
bl entry
nop
stxv 34, 128(1)
# <rest of function>and a copy of the Power ISA manual, the miscompilation appears to be in the entry function. The 128-bit integer is passed in GPR 3 and 4. The |
efriedma-quic
added
the
good first issue
|
Hi! This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:
If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below. |
|
@llvm/issue-subscribers-good-first-issue Author: Trevor Gross (tgross35)
Doing a roundtrip i128 -> f128 -> i128 should work but it appears to be broken when the calls are external, possibly depending on some optimizations. It seems like the `f128`/`i128` is getting split into two 64-bit values, which are getting reversed at some point. The problem does not seem to happen without enabling the pwr9 target feature.
Originally identified with rust in rust-lang/rust#125102. Source files: // transmute_lib.rs
#![feature(f128)]
#![allow(improper_ctypes_definitions)] // ok since llvm 18
use std::mem::transmute;
#[no_mangle]
pub extern "C" fn entry(a: u128) -> f128 {
unsafe { transmute::<u128, f128>(a) }
}// transmute_call_lib.rs
#![feature(f128)]
#![allow(improper_ctypes)] // ok since llvm 18
extern crate transmute_lib;
use std::mem::transmute;
use std::process::exit;
extern "C" {
fn entry(a: u128) -> f128;
}
fn main() {
let a = unsafe { entry(0x1) }; // bitcast in an external function
let res = unsafe { transmute::<f128, u128>(a) }; // bitcast back
if res == 0x1 {
exit(0); // correct
} else if res == 0x1 << 64 {
exit(1); // incorrect value with endianness flipped
} else {
exit(2); // unexpected value
}
}Versions: Compilation: Execution: The above should output 0. Full IR: <details> ; ModuleID = 'transmute_lib.1e179323af95c5c5-cgu.0'
source_filename = "transmute_lib.1e179323af95c5c5-cgu.0"
target datalayout = "E-m:e-Fi64-i64:64-n32:64-S128-v256:256:256-v512:512:512"
target triple = "powerpc64-unknown-linux-gnu"
; Function Attrs: uwtable
define fp128 @<!-- -->entry(i128 %a) unnamed_addr #<!-- -->0 {
start:
%_0 = bitcast i128 %a to fp128
ret fp128 %_0
}
attributes #<!-- -->0 = { uwtable "probe-stack"="inline-asm" "target-cpu"="pwr9" }
!llvm.module.flags = !{!0}
!llvm.ident = !{!1}
!0 = !{i32 8, !"PIC Level", i32 2}
!1 = !{!"rustc version 1.80.0-nightly (9c9b56879 2024-05-05)"}</details> <details> The only relevant part is in ; ModuleID = 'transmute_call_lib.1791869a4d73965-cgu.0'
source_filename = "transmute_call_lib.1791869a4d73965-cgu.0"
target datalayout = "E-m:e-Fi64-i64:64-n32:64-S128-v256:256:256-v512:512:512"
target triple = "powerpc64-unknown-linux-gnu"
@<!-- -->vtable.0 = private unnamed_addr constant <{ ptr, [16 x i8], ptr, ptr, ptr }> <{ ptr @"_ZN4core3ptr85drop_in_place$LT$std..rt..lan
; std::sys_common::backtrace::__rust_begin_short_backtrace
; Function Attrs: noinline uwtable
define internal void @<!-- -->_ZN3std10sys_common9backtrace28__rust_begin_short_backtrace17hf94855fdbb5829c5E(ptr %f) unnamed_addr #<!-- -->0 {
start:
; call core::ops::function::FnOnce::call_once
call void @<!-- -->_ZN4core3ops8function6FnOnce9call_once17h3056e9bd87d66482E(ptr %f)
call void asm sideeffect "", "~{memory}"(), !srcloc !3
ret void
}
; std::rt::lang_start
; Function Attrs: uwtable
define hidden i64 @<!-- -->_ZN3std2rt10lang_start17hdc6989dbc5702db1E(ptr %main, i64 %argc, ptr %argv, i8 %sigpipe) unnamed_addr #<!-- -->1 {
start:
%_8 = alloca [8 x i8], align 8
%_5 = alloca [8 x i8], align 8
store ptr %main, ptr %_8, align 8
; call std::rt::lang_start_internal
%0 = call i64 @<!-- -->_ZN3std2rt19lang_start_internal17he440c14c55fd4760E(ptr align 1 %_8, ptr align 8 @<!-- -->vtable.0, i64 %argc, ptr %argv,
store i64 %0, ptr %_5, align 8
%v = load i64, ptr %_5, align 8
ret i64 %v
}
; std::rt::lang_start::{{closure}}
; Function Attrs: inlinehint uwtable
define internal i32 @"_ZN3std2rt10lang_start28_$u7b$$u7b$closure$u7d$$u7d$17hdb386b686ec8565dE"(ptr align 8 %_1) unnamed_addr #<!-- -->2 {
start:
%self = alloca [1 x i8], align 1
%_4 = load ptr, ptr %_1, align 8
; call std::sys_common::backtrace::__rust_begin_short_backtrace
call void @<!-- -->_ZN3std10sys_common9backtrace28__rust_begin_short_backtrace17hf94855fdbb5829c5E(ptr %_4)
; call <() as std::process::Termination>::report
%0 = call i8 @"_ZN54_$LT$$LP$$RP$$u20$as$u20$std..process..Termination$GT$6report17h3606faab680ab85fE"()
store i8 %0, ptr %self, align 1
%_6 = load i8, ptr %self, align 1
%_0 = zext i8 %_6 to i32
ret i32 %_0
}
; core::ops::function::FnOnce::call_once{{vtable.shim}}
; Function Attrs: inlinehint uwtable
define internal i32 @"_ZN4core3ops8function6FnOnce40call_once$u7b$$u7b$vtable.shim$u7d$$u7d$17h956497c27ef6ef7fE"(ptr %_1) unnamed
start:
%_2 = alloca [0 x i8], align 1
%0 = load ptr, ptr %_1, align 8
; call core::ops::function::FnOnce::call_once
%_0 = call i32 @<!-- -->_ZN4core3ops8function6FnOnce9call_once17h9737a54d47c05e22E(ptr %0)
ret i32 %_0
}
; core::ops::function::FnOnce::call_once
; Function Attrs: inlinehint uwtable
define internal void @<!-- -->_ZN4core3ops8function6FnOnce9call_once17h3056e9bd87d66482E(ptr %_1) unnamed_addr #<!-- -->2 {
start:
%_2 = alloca [0 x i8], align 1
call void %_1()
ret void
}
; core::ops::function::FnOnce::call_once
; Function Attrs: inlinehint uwtable
define internal i32 @<!-- -->_ZN4core3ops8function6FnOnce9call_once17h9737a54d47c05e22E(ptr %0) unnamed_addr #<!-- -->2 personality ptr @<!-- -->rust_eh_p
start:
%1 = alloca [16 x i8], align 8
%_2 = alloca [0 x i8], align 1
%_1 = alloca [8 x i8], align 8
store ptr %0, ptr %_1, align 8
; invoke std::rt::lang_start::{{closure}}
%_0 = invoke i32 @"_ZN3std2rt10lang_start28_$u7b$$u7b$closure$u7d$$u7d$17hdb386b686ec8565dE"(ptr align 8 %_1)
to label %bb1 unwind label %cleanup
bb3: ; preds = %cleanup
%2 = load ptr, ptr %1, align 8
%3 = getelementptr inbounds i8, ptr %1, i64 8
%4 = load i32, ptr %3, align 8
%5 = insertvalue { ptr, i32 } poison, ptr %2, 0
%6 = insertvalue { ptr, i32 } %5, i32 %4, 1
resume { ptr, i32 } %6
cleanup: ; preds = %start
%7 = landingpad { ptr, i32 }
cleanup
%8 = extractvalue { ptr, i32 } %7, 0
%9 = extractvalue { ptr, i32 } %7, 1
store ptr %8, ptr %1, align 8
%10 = getelementptr inbounds i8, ptr %1, i64 8
store i32 %9, ptr %10, align 8
br label %bb3
bb1: ; preds = %start
ret i32 %_0
}
; core::ptr::drop_in_place<std::rt::lang_start<()>::{{closure}}>
; Function Attrs: inlinehint uwtable
define internal void @"_ZN4core3ptr85drop_in_place$LT$std..rt..lang_start$LT$$LP$$RP$$GT$..$u7b$$u7b$closure$u7d$$u7d$$GT$17h64db6
start:
ret void
}
; <() as std::process::Termination>::report
; Function Attrs: inlinehint uwtable
define internal i8 @"_ZN54_$LT$$LP$$RP$$u20$as$u20$std..process..Termination$GT$6report17h3606faab680ab85fE"() unnamed_addr #<!-- -->2 {
start:
ret i8 0
}
; transmute_call_lib::main
; Function Attrs: uwtable
define internal void @<!-- -->_ZN18transmute_call_lib4main17hfa19d9d60e61b95dE() unnamed_addr #<!-- -->1 {
start:
%a = call fp128 @<!-- -->entry(i128 1)
%res = bitcast fp128 %a to i128
%0 = icmp eq i128 %res, 1
br i1 %0, label %bb2, label %bb3
bb2: ; preds = %start
; call std::process::exit
call void @<!-- -->_ZN3std7process4exit17hb2f96155fda111fdE(i32 0) #<!-- -->5
unreachable
bb3: ; preds = %start
%_4 = icmp eq i128 %res, 18446744073709551616
br i1 %_4, label %bb5, label %bb6
bb6: ; preds = %bb3
; call std::process::exit
call void @<!-- -->_ZN3std7process4exit17hb2f96155fda111fdE(i32 2) #<!-- -->5
unreachable
bb5: ; preds = %bb3
; call std::process::exit
call void @<!-- -->_ZN3std7process4exit17hb2f96155fda111fdE(i32 1) #<!-- -->5
unreachable
}
; std::rt::lang_start_internal
; Function Attrs: uwtable
declare i64 @<!-- -->_ZN3std2rt19lang_start_internal17he440c14c55fd4760E(ptr align 1, ptr align 8, i64, ptr, i8) unnamed_addr #<!-- -->1
; Function Attrs: uwtable
declare zeroext i32 @<!-- -->rust_eh_personality(i32 signext, i32 zeroext, i64, ptr, ptr) unnamed_addr #<!-- -->1
; Function Attrs: uwtable
declare fp128 @<!-- -->entry(i128) unnamed_addr #<!-- -->1
; std::process::exit
; Function Attrs: noreturn uwtable
declare void @<!-- -->_ZN3std7process4exit17hb2f96155fda111fdE(i32) unnamed_addr #<!-- -->3
define i32 @<!-- -->main(i32 %0, ptr %1) unnamed_addr #<!-- -->4 {
top:
%2 = sext i32 %0 to i64
; call std::rt::lang_start
%3 = call i64 @<!-- -->_ZN3std2rt10lang_start17hdc6989dbc5702db1E(ptr @<!-- -->_ZN18transmute_call_lib4main17hfa19d9d60e61b95dE, i64 %2, ptr %1, i8 0)
%4 = trunc i64 %3 to i32
ret i32 %4
}
attributes #<!-- -->0 = { noinline uwtable "probe-stack"="inline-asm" "target-cpu"="pwr9" }
attributes #<!-- -->1 = { uwtable "probe-stack"="inline-asm" "target-cpu"="pwr9" }
attributes #<!-- -->2 = { inlinehint uwtable "probe-stack"="inline-asm" "target-cpu"="pwr9" }
attributes #<!-- -->3 = { noreturn uwtable "probe-stack"="inline-asm" "target-cpu"="pwr9" }
attributes #<!-- -->4 = { "target-cpu"="pwr9" }
attributes #<!-- -->5 = { noreturn }
!llvm.module.flags = !{!0, !1}
!llvm.ident = !{!2}
!0 = !{i32 8, !"PIC Level", i32 2}
!1 = !{i32 7, !"PIE Level", i32 2}
!2 = !{!"rustc version 1.80.0-nightly (9c9b56879 2024-05-05)"}
!3 = !{i32 1628919}</details> This could be indirectly related to #92233 (comment) since that needs use of |
llvmbot
pushed a commit
to llvmbot/llvm-project
that referenced
this issue
Aug 22, 2024
Fixes llvm#92246 Match the behaviour of `bitcast v2i64 (BUILD_PAIR %lo %hi)` when encountering `bitcast fp128 (BUILD_PAIR %lo $hi)`. by inserting a missing swap of the arguments based on endianness. ### Current behaviour: **fp128** bitcast fp128 (BUILD_PAIR %lo $hi) => BUILD_FP128 %lo %hi BUILD_FP128 %lo %hi => MTVSRDD %hi %lo **v2i64** bitcast v2i64 (BUILD_PAIR %lo %hi) => BUILD_VECTOR %hi %lo BUILD_VECTOR %hi %lo => MTVSRDD %lo %hi (cherry picked from commit 408d82d)
tru
pushed a commit
to llvmbot/llvm-project
that referenced
this issue
Sep 1, 2024
Fixes llvm#92246 Match the behaviour of `bitcast v2i64 (BUILD_PAIR %lo %hi)` when encountering `bitcast fp128 (BUILD_PAIR %lo $hi)`. by inserting a missing swap of the arguments based on endianness. ### Current behaviour: **fp128** bitcast fp128 (BUILD_PAIR %lo $hi) => BUILD_FP128 %lo %hi BUILD_FP128 %lo %hi => MTVSRDD %hi %lo **v2i64** bitcast v2i64 (BUILD_PAIR %lo %hi) => BUILD_VECTOR %hi %lo BUILD_VECTOR %hi %lo => MTVSRDD %lo %hi (cherry picked from commit 408d82d)
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Doing a roundtrip i128 -> f128 -> i128 should work but it appears to be broken when the calls are external, possibly depending on some optimizations. It seems like the
f128/i128is getting split into two 64-bit values, which are getting reversed at some point. The problem does not seem to happen without enabling the pwr9 target feature.Originally identified with rust in rust-lang/rust#125102. Source files:
Versions:
Compilation:
Execution:
The above should output 0. Full IR:
Library function
Executable
The only relevant part is in
transmute_call_lib::mainThis could be indirectly related to #92233 (comment) since that needs use of
f128to cause the crash.The text was updated successfully, but these errors were encountered: