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[DAG] Make strictfp attribute only restricts for libm and make non-math optimizations possible #165464

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[DAG] Make strictfp attribute only restricts for libm and make non-math optimizations possible #165464

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a40b5e1
let strictfp only work for libm
diggerlin Oct 28, 2025
44c7bad
add comment to add test caee for fp-strict
diggerlin Nov 4, 2025
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15 changes: 9 additions & 6 deletions llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9392,7 +9392,9 @@ bool SelectionDAGBuilder::visitStrNLenCall(const CallInst &I) {
bool SelectionDAGBuilder::visitUnaryFloatCall(const CallInst &I,
unsigned Opcode) {
// We already checked this call's prototype; verify it doesn't modify errno.
if (!I.onlyReadsMemory())
// Do not perform optimizations for call sites that require strict
// floating-point semantics.
if (!I.onlyReadsMemory() || I.isStrictFP())
return false;

SDNodeFlags Flags;
Expand All @@ -9412,7 +9414,9 @@ bool SelectionDAGBuilder::visitUnaryFloatCall(const CallInst &I,
bool SelectionDAGBuilder::visitBinaryFloatCall(const CallInst &I,
unsigned Opcode) {
// We already checked this call's prototype; verify it doesn't modify errno.
if (!I.onlyReadsMemory())
// Do not perform optimizations for call sites that require strict
// floating-point semantics.
if (!I.onlyReadsMemory() || I.isStrictFP())
return false;

SDNodeFlags Flags;
Expand Down Expand Up @@ -9445,11 +9449,10 @@ void SelectionDAGBuilder::visitCall(const CallInst &I) {

// Check for well-known libc/libm calls. If the function is internal, it
// can't be a library call. Don't do the check if marked as nobuiltin for
// some reason or the call site requires strict floating point semantics.
// some reason.
LibFunc Func;
if (!I.isNoBuiltin() && !I.isStrictFP() && !F->hasLocalLinkage() &&
F->hasName() && LibInfo->getLibFunc(*F, Func) &&
LibInfo->hasOptimizedCodeGen(Func)) {
if (!I.isNoBuiltin() && !F->hasLocalLinkage() && F->hasName() &&
LibInfo->getLibFunc(*F, Func) && LibInfo->hasOptimizedCodeGen(Func)) {
switch (Func) {
default: break;
case LibFunc_bcmp:
Expand Down
34 changes: 34 additions & 0 deletions llvm/test/CodeGen/PowerPC/milicode32.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -68,4 +68,38 @@ entry:
ret i32 %call
}

define i32 @strlen_test_fp_strict(ptr noundef %str) nounwind {
; CHECK-AIX-32-P9-LABEL: strlen_test_fp_strict:
; CHECK-AIX-32-P9: # %bb.0: # %entry
; CHECK-AIX-32-P9-NEXT: mflr r0
; CHECK-AIX-32-P9-NEXT: stwu r1, -64(r1)
; CHECK-AIX-32-P9-NEXT: stw r0, 72(r1)
; CHECK-AIX-32-P9-NEXT: stw r3, 60(r1)
; CHECK-AIX-32-P9-NEXT: bl .___strlen[PR]
; CHECK-AIX-32-P9-NEXT: nop
; CHECK-AIX-32-P9-NEXT: addi r1, r1, 64
; CHECK-AIX-32-P9-NEXT: lwz r0, 8(r1)
; CHECK-AIX-32-P9-NEXT: mtlr r0
; CHECK-AIX-32-P9-NEXT: blr
;
; CHECK-LINUX32-P9-LABEL: strlen_test_fp_strict:
; CHECK-LINUX32-P9: # %bb.0: # %entry
; CHECK-LINUX32-P9-NEXT: mflr r0
; CHECK-LINUX32-P9-NEXT: stwu r1, -16(r1)
; CHECK-LINUX32-P9-NEXT: stw r0, 20(r1)
; CHECK-LINUX32-P9-NEXT: stw r3, 12(r1)
; CHECK-LINUX32-P9-NEXT: bl strlen
; CHECK-LINUX32-P9-NEXT: lwz r0, 20(r1)
; CHECK-LINUX32-P9-NEXT: addi r1, r1, 16
; CHECK-LINUX32-P9-NEXT: mtlr r0
; CHECK-LINUX32-P9-NEXT: blr
entry:
%str.addr = alloca ptr, align 4
store ptr %str, ptr %str.addr, align 4
%0 = load ptr, ptr %str.addr, align 4
%call = call i32 @strlen(ptr noundef %0) #0
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@arsenm arsenm Nov 3, 2025

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Should add test, not modify existing one

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@arsenm arsenm Nov 4, 2025

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bump

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@diggerlin diggerlin Nov 5, 2025

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I’ve added a new test scenario called strlen_test_fp_strict , which differs from strlen_test.
there is

%call = call i32 @strlen(ptr noundef %0) #0 
attributes #0 = { strictfp }

in the strlen_test_fp_strict.
I’m not entirely sure what “bump” refers to in this context. could you please clarify its meaning?

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@diggerlin diggerlin Nov 6, 2025

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Whenever you have a moment, could you please take another look and let me know your thoughts —especially regarding the “bump” reference I mentioned?
Thanks for your time! @arsenm

ret i32 %call
}

declare i32 @strlen(ptr noundef) nounwind
attributes #0 = { strictfp }