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[IPSCCP][FuncSpec] Protect against metadata access from call args. #124284

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Merged
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Jan 25, 2025
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[IPSCCP][FuncSpec] Protect against metadata access from call args. #124284

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2 changes: 2 additions & 0 deletions llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -415,6 +415,8 @@ Constant *InstCostVisitor::visitCallBase(CallBase &I) {

for (unsigned Idx = 0, E = I.getNumOperands() - 1; Idx != E; ++Idx) {
Value *V = I.getOperand(Idx);
if (isa<MetadataAsValue>(V))
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Should perhaps ConstantFoldCall be handling this?

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I believe it is the findConstantFor -> getLatticeValueFor call that causes the problem, as the value is not in the lattice.

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Then should the isa(V) be moved inside findConstantFor?

if (isa<MetadataAsValue>(V))
  return nullptr;
if (auto *C = dyn_cast<Constant>(V))
  return C;
...

Would a metadata operand be possible to appear in anything else other than a call? If not, then let's leave it as is.

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I was wondering that - but calls should be the most common place. For other operations like load / stores the metadata will be an extra operands, not one of the ones we are already looking at like the Value or Pointer.
I believe this is where they are excluded for normal SCCP:

llvm-project/llvm/lib/Transforms/Utils/SCCPSolver.cpp

Line 1796 in 544a3cb

if (A.get()->getType()->isMetadataTy())

return nullptr;
Constant *C = findConstantFor(V);
if (!C)
return nullptr;
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17 changes: 17 additions & 0 deletions llvm/test/Transforms/FunctionSpecialization/solver-constant-strictfpmetadata.ll
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@@ -0,0 +1,17 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt -passes=ipsccp -force-specialization -S < %s | FileCheck %s

define float @test(ptr %this, float %cm, i1 %0) strictfp {
; CHECK-LABEL: define float @test(
; CHECK-SAME: ptr [[THIS:%.*]], float [[CM:%.*]], i1 [[TMP0:%.*]]) #[[ATTR0:[0-9]+]] {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[CMP:%.*]] = call i1 @llvm.experimental.constrained.fcmps.f32(float [[CM]], float 0.000000e+00, metadata !"ole", metadata !"fpexcept.strict")
; CHECK-NEXT: [[CALL295:%.*]] = call float @test.specialized.1(ptr null, float 0.000000e+00, i1 false)
; CHECK-NEXT: ret float 0.000000e+00
;
entry:
%cmp = call i1 @llvm.experimental.constrained.fcmps.f32(float %cm, float 0.000000e+00, metadata !"ole", metadata !"fpexcept.strict") #0
%call295 = call float @test(ptr null, float 0.000000e+00, i1 false) #0
ret float 0.000000e+00
}

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