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[clang] Enable FPContract with optnone #91061

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merged 2 commits into from
May 6, 2024
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[clang] Enable FPContract with optnone #91061

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32c0ec8
[clang] Enable FPContract with optnone
spavloff May 4, 2024
e518bbf
Fix clang-format errors
spavloff May 4, 2024
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5 changes: 1 addition & 4 deletions clang/include/clang/Basic/LangOptions.h
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Expand Up @@ -968,10 +968,7 @@ class FPOptionsOverride {
setAllowFPContractAcrossStatement();
}

void setDisallowOptimizations() {
setFPPreciseEnabled(true);
setDisallowFPContract();
}
void setDisallowOptimizations() { setFPPreciseEnabled(true); }
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Actually, instead of just removing the call to setDisallowFPContract(), we should instead explicitly set the FP Contraction state to "on" (which is the default at -O0). That is, we should call setAllowFPContractWithinStatement().

In particular, if the user is compiling with -ffast-math, then the FP Contraction state will be -ffp-contract=fast (allowing FMA across multiple statements). And if they applied optnone, then by removing the call to setDisallowFPContract(), we would mistakenly leave that inter-statement FMA enabled. By calling setAllowFPContractWithinStatement() we are explicitly setting it the equivalent of the command-line option -ffp-contract=on, which is the desired state of -O0 (and optnone).

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Actually this is done by the call to setFPPreciseEnabled: https://github.com/spavloff/llvm-project/blob/e518bbfed9eefbe6d9d952dd0354ee974f7a9305/clang/include/clang/Basic/LangOptions.h#L955-L969

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Ahhh.. I didn't realize. Thanks!


storage_type getAsOpaqueInt() const {
return (static_cast<storage_type>(Options.getAsOpaqueInt())
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18 changes: 9 additions & 9 deletions clang/test/AST/ast-dump-fpfeatures.cpp
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Expand Up @@ -198,7 +198,7 @@ float func_19(float x, float y) {
// CHECK-LABEL: FunctionDecl {{.*}} func_19 'float (float, float)'
// CHECK: CompoundStmt {{.*}} MathErrno=1
// CHECK: ReturnStmt
// CHECK: BinaryOperator {{.*}} 'float' '+' ConstRoundingMode=downward MathErrno=1
// CHECK: BinaryOperator {{.*}} 'float' '+' FPContractMode=1 ConstRoundingMode=downward MathErrno=1

__attribute__((optnone))
float func_20(float x, float y) try {
Expand All @@ -210,7 +210,7 @@ float func_20(float x, float y) try {
// CHECK-LABEL: FunctionDecl {{.*}} func_20 'float (float, float)'
// CHECK: CompoundStmt {{.*}} ConstRoundingMode=downward MathErrno=1
// CHECK: ReturnStmt
// CHECK: BinaryOperator {{.*}} 'float' '+' ConstRoundingMode=downward MathErrno=1
// CHECK: BinaryOperator {{.*}} 'float' '+' FPContractMode=1 ConstRoundingMode=downward MathErrno=1

struct C21 {
C21(float x, float y);
Expand All @@ -221,15 +221,15 @@ struct C21 {
};

// CHECK-LABEL: CXXMethodDecl {{.*}} a_method 'float (float, float)'
// CHECK: CompoundStmt {{.*}} ConstRoundingMode=downward MathErrno=1
// CHECK: CompoundStmt {{.*}} FPContractMode=1 ConstRoundingMode=downward MathErrno=1
// CHECK: ReturnStmt
// CHECK: BinaryOperator {{.*}} 'float' '*' ConstRoundingMode=downward MathErrno=1
// CHECK: BinaryOperator {{.*}} 'float' '*' FPContractMode=1 ConstRoundingMode=downward MathErrno=1

__attribute__((optnone)) C21::C21(float x, float y) : member(x + y) {}

// CHECK-LABEL: CXXConstructorDecl {{.*}} C21 'void (float, float)'
// CHECK: CXXCtorInitializer {{.*}} 'member' 'float'
// CHECK: BinaryOperator {{.*}} 'float' '+' ConstRoundingMode=downward MathErrno=1
// CHECK: BinaryOperator {{.*}} 'float' '+' FPContractMode=1 ConstRoundingMode=downward MathErrno=1

template <typename T>
__attribute__((optnone)) T func_22(T x, T y) {
Expand All @@ -238,13 +238,13 @@ __attribute__((optnone)) T func_22(T x, T y) {

// CHECK-LABEL: FunctionTemplateDecl {{.*}} func_22
// CHECK: FunctionDecl {{.*}} func_22 'T (T, T)'
// CHECK: CompoundStmt {{.*}} ConstRoundingMode=downward MathErrno=1
// CHECK: CompoundStmt {{.*}} FPContractMode=1 ConstRoundingMode=downward MathErrno=1
// CHECK: ReturnStmt
// CHECK: BinaryOperator {{.*}} '+' ConstRoundingMode=downward MathErrno=1
// CHECK: BinaryOperator {{.*}} '+' FPContractMode=1 ConstRoundingMode=downward MathErrno=1
// CHECK: FunctionDecl {{.*}} func_22 'float (float, float)'
// CHECK: CompoundStmt {{.*}} ConstRoundingMode=downward MathErrno=1
// CHECK: CompoundStmt {{.*}} FPContractMode=1 ConstRoundingMode=downward MathErrno=1
// CHECK: ReturnStmt
// CHECK: BinaryOperator {{.*}} 'float' '+' ConstRoundingMode=downward MathErrno=1
// CHECK: BinaryOperator {{.*}} 'float' '+' FPContractMode=1 ConstRoundingMode=downward MathErrno=1

float func_23(float x, float y) {
return func_22(x, y);
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4 changes: 2 additions & 2 deletions clang/test/AST/ast-dump-fpfeatures.m
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Expand Up @@ -24,6 +24,6 @@ - (float) sum: (float)x with: (float)y __attribute((optnone)) {

// CHECK-LABEL: ObjCImplementationDecl {{.*}} Adder
// CHECK: ObjCMethodDecl {{.*}} - sum:with: 'float'
// CHECK: CompoundStmt {{.*}} MathErrno=1
// CHECK: CompoundStmt {{.*}} FPContractMode=1 MathErrno=1
// CHECK-NEXT: ReturnStmt
// CHECK-NEXT: BinaryOperator {{.*}} 'float' '+' MathErrno=1
// CHECK-NEXT: BinaryOperator {{.*}} 'float' '+' FPContractMode=1 MathErrno=1
8 changes: 4 additions & 4 deletions clang/test/AST/ast-dump-late-parsing.cpp
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Expand Up @@ -11,13 +11,13 @@ __attribute__((optnone)) T func_22(T x, T y) {

// CHECK-LABEL: FunctionTemplateDecl {{.*}} func_22
// CHECK: FunctionDecl {{.*}} func_22 'T (T, T)'
// CHECK: CompoundStmt {{.*}} ConstRoundingMode=downward MathErrno=1
// CHECK: CompoundStmt {{.*}} FPContractMode=1 ConstRoundingMode=downward MathErrno=1
// CHECK: ReturnStmt
// CHECK: BinaryOperator {{.*}} '+' ConstRoundingMode=downward MathErrno=1
// CHECK: BinaryOperator {{.*}} '+' FPContractMode=1 ConstRoundingMode=downward MathErrno=1
// CHECK: FunctionDecl {{.*}} func_22 'float (float, float)'
// CHECK: CompoundStmt {{.*}} ConstRoundingMode=downward MathErrno=1
// CHECK: CompoundStmt {{.*}} FPContractMode=1 ConstRoundingMode=downward MathErrno=1
// CHECK: ReturnStmt
// CHECK: BinaryOperator {{.*}} 'float' '+' ConstRoundingMode=downward MathErrno=1
// CHECK: BinaryOperator {{.*}} 'float' '+' FPContractMode=1 ConstRoundingMode=downward MathErrno=1

float func_23(float x, float y) {
return func_22(x, y);
Expand Down