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Closed by commit rG9fd4f80e33a4: [ConstantFolding] Unify handling of load from
uniform value (authored by nikic).
Herald added a project: clang.
Herald added a subscriber: cfe-commits.
Changed prior to commit:
https://reviews.llvm.org/D115924?vs=395126&id=395136#toc
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D115924/new/
https://reviews.llvm.org/D115924
Files:
clang/test/CodeGen/aapcs-align.cpp
llvm/include/llvm/Analysis/ConstantFolding.h
llvm/lib/Analysis/ConstantFolding.cpp
llvm/lib/Transforms/IPO/GlobalOpt.cpp
llvm/test/Transforms/GlobalOpt/x86_mmx_load.ll
llvm/test/Transforms/InstSimplify/ConstProp/loads.ll
Index: llvm/test/Transforms/InstSimplify/ConstProp/loads.ll
===================================================================
--- llvm/test/Transforms/InstSimplify/ConstProp/loads.ll
+++ llvm/test/Transforms/InstSimplify/ConstProp/loads.ll
@@ -280,3 +280,16 @@
%v = load { i64, i64 }, { i64, i64 }* @g3
ret { i64, i64 } %v
}
+
+@m64 = internal constant [2 x i64] zeroinitializer
+@idx = external global i32
+
+; This should not try to create an x86_mmx null value.
+define x86_mmx @load_mmx() {
+; CHECK-LABEL: @load_mmx(
+; CHECK-NEXT: [[TEMP:%.*]] = load x86_mmx, x86_mmx* bitcast (i64* getelementptr ([2 x i64], [2 x i64]* @m64, i64 0, i64 ptrtoint (i32* @idx to i64)) to x86_mmx*), align 8
+; CHECK-NEXT: ret x86_mmx [[TEMP]]
+;
+ %temp = load x86_mmx, x86_mmx* bitcast (i64* getelementptr ([2 x i64], [2 x i64]* @m64, i64 0, i64 ptrtoint (i32* @idx to i64)) to x86_mmx*)
+ ret x86_mmx %temp
+}
Index: llvm/test/Transforms/GlobalOpt/x86_mmx_load.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/GlobalOpt/x86_mmx_load.ll
@@ -0,0 +1,12 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -globalopt < %s | FileCheck %s
+
+@m64 = internal global <1 x i64> zeroinitializer
+
+define i32 @load_mmx() {
+; CHECK-LABEL: @load_mmx(
+; CHECK-NEXT: ret i32 0
+;
+ %temp = load x86_mmx, x86_mmx* bitcast (<1 x i64>* @m64 to x86_mmx*)
+ ret i32 0
+}
Index: llvm/lib/Transforms/IPO/GlobalOpt.cpp
===================================================================
--- llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -305,8 +305,9 @@
else if (auto *LI = dyn_cast<LoadInst>(U)) {
// A load from zeroinitializer is always zeroinitializer, regardless of
// any applied offset.
- if (Init->isNullValue()) {
- LI->replaceAllUsesWith(Constant::getNullValue(LI->getType()));
+ if (Constant *Res =
+ ConstantFoldLoadFromUniformValue(Init, LI->getType())) {
+ LI->replaceAllUsesWith(Res);
EraseFromParent(LI);
continue;
}
Index: llvm/lib/Analysis/ConstantFolding.cpp
===================================================================
--- llvm/lib/Analysis/ConstantFolding.cpp
+++ llvm/lib/Analysis/ConstantFolding.cpp
@@ -106,11 +106,8 @@
"Invalid constantexpr bitcast!");
// Catch the obvious splat cases.
- if (C->isNullValue() && !DestTy->isX86_MMXTy() && !DestTy->isX86_AMXTy())
- return Constant::getNullValue(DestTy);
- if (C->isAllOnesValue() && !DestTy->isX86_MMXTy() && !DestTy->isX86_AMXTy() &&
- !DestTy->isPtrOrPtrVectorTy()) // Don't get ones for ptr types!
- return Constant::getAllOnesValue(DestTy);
+ if (Constant *Res = ConstantFoldLoadFromUniformValue(C, DestTy))
+ return Res;
if (auto *VTy = dyn_cast<VectorType>(C->getType())) {
// Handle a vector->scalar integer/fp cast.
@@ -362,16 +359,8 @@
// Catch the obvious splat cases (since all-zeros can coerce non-integral
// pointers legally).
- if (C->isNullValue() && !DestTy->isX86_MMXTy() && !DestTy->isX86_AMXTy())
- return Constant::getNullValue(DestTy);
- if (C->isAllOnesValue() &&
- (DestTy->isIntegerTy() || DestTy->isFloatingPointTy() ||
- DestTy->isVectorTy()) &&
- !DestTy->isX86_AMXTy() && !DestTy->isX86_MMXTy() &&
- !DestTy->isPtrOrPtrVectorTy())
- // Get ones when the input is trivial, but
- // only for supported types inside getAllOnesValue.
- return Constant::getAllOnesValue(DestTy);
+ if (Constant *Res = ConstantFoldLoadFromUniformValue(C, DestTy))
+ return Res;
// If the type sizes are the same and a cast is legal, just directly
// cast the constant.
@@ -704,16 +693,13 @@
Offset, DL))
return Result;
- // If this load comes from anywhere in a constant global, and if the global
- // is all undef or zero, we know what it loads.
- if (auto *GV = dyn_cast<GlobalVariable>(getUnderlyingObject(C))) {
- if (GV->isConstant() && GV->hasDefinitiveInitializer()) {
- if (GV->getInitializer()->isNullValue())
- return Constant::getNullValue(Ty);
- if (isa<UndefValue>(GV->getInitializer()))
- return UndefValue::get(Ty);
- }
- }
+ // If this load comes from anywhere in a uniform constant global, the value
+ // is always the same, regardless of the loaded offset.
+ if (auto *GV = dyn_cast<GlobalVariable>(getUnderlyingObject(C)))
+ if (GV->isConstant() && GV->hasDefinitiveInitializer())
+ if (Constant *Res =
+ ConstantFoldLoadFromUniformValue(GV->getInitializer(), Ty))
+ return Res;
return nullptr;
}
@@ -724,6 +710,19 @@
return ConstantFoldLoadFromConstPtr(C, Ty, Offset, DL);
}
+Constant *llvm::ConstantFoldLoadFromUniformValue(Constant *C, Type *Ty) {
+ if (isa<PoisonValue>(C))
+ return PoisonValue::get(Ty);
+ if (isa<UndefValue>(C))
+ return UndefValue::get(Ty);
+ if (C->isNullValue() && !Ty->isX86_MMXTy() && !Ty->isX86_AMXTy())
+ return Constant::getNullValue(Ty);
+ if (C->isAllOnesValue() &&
+ (Ty->isIntOrIntVectorTy() || Ty->isFPOrFPVectorTy()))
+ return Constant::getAllOnesValue(Ty);
+ return nullptr;
+}
+
namespace {
/// One of Op0/Op1 is a constant expression.
Index: llvm/include/llvm/Analysis/ConstantFolding.h
===================================================================
--- llvm/include/llvm/Analysis/ConstantFolding.h
+++ llvm/include/llvm/Analysis/ConstantFolding.h
@@ -148,6 +148,12 @@
Constant *ConstantFoldLoadFromConstPtr(Constant *C, Type *Ty,
const DataLayout &DL);
+/// If C is a uniform value where all bits are the same (either all zero, all
+/// ones, all undef or all poison), return the corresponding uniform value in
+/// the new type. If the value is not uniform or the result cannot be
+/// represented, return null.
+Constant *ConstantFoldLoadFromUniformValue(Constant *C, Type *Ty);
+
/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
/// getelementptr constantexpr, return the constant value being addressed by the
/// constant expression, or null if something is funny and we can't decide.
Index: clang/test/CodeGen/aapcs-align.cpp
===================================================================
--- clang/test/CodeGen/aapcs-align.cpp
+++ clang/test/CodeGen/aapcs-align.cpp
@@ -134,8 +134,8 @@
f6m(1, 2, 3, 4, 5, s);
}
// CHECK: define{{.*}} void @g6
-// CHECK: call void @f6(i32 1, [4 x i32] [i32 6, i32 7, i32 0, i32 0])
-// CHECK: call void @f6m(i32 1, i32 2, i32 3, i32 4, i32 5, [4 x i32] [i32 6, i32 7, i32 0, i32 0])
+// CHECK: call void @f6(i32 1, [4 x i32] [i32 6, i32 7, i32 0, i32 undef])
+// CHECK: call void @f6m(i32 1, i32 2, i32 3, i32 4, i32 5, [4 x i32] [i32 6, i32 7, i32 0, i32 undef])
// CHECK: declare void @f6(i32, [4 x i32])
// CHECK: declare void @f6m(i32, i32, i32, i32, i32, [4 x i32])
}
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