[clang] Fix bug with -ffp-contract=fast-honor-pragmas (PR #104857)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Andy Kaylor (andykaylor)

<details>
<summary>Changes</summary>

This fixes a problem which caused clang to assert in the Sema pragma
handling if it encountered "#pragma STDC FP_CONTRACT DEFAULT" when
compiling with the -ffp-contract=fast-honor-pragmas option.

This fixes https://github.com/llvm/llvm-project/issues/104830


---
Full diff: https://github.com/llvm/llvm-project/pull/104857.diff


3 Files Affected:

- (modified) clang/lib/Sema/SemaAttr.cpp (+1-2) 
- (added) clang/test/CodeGen/ffp-contract-fast-honor-pramga-option.cpp (+37) 
- (added) clang/test/CodeGen/ffp-contract-fhp-pragma-override.cpp (+151) 


``````````diff
diff --git a/clang/lib/Sema/SemaAttr.cpp b/clang/lib/Sema/SemaAttr.cpp
index b0c239678d0b0..a1724820472b5 100644
--- a/clang/lib/Sema/SemaAttr.cpp
+++ b/clang/lib/Sema/SemaAttr.cpp
@@ -1269,13 +1269,12 @@ void Sema::ActOnPragmaFPContract(SourceLocation Loc,
     NewFPFeatures.setAllowFPContractWithinStatement();
     break;
   case LangOptions::FPM_Fast:
+  case LangOptions::FPM_FastHonorPragmas:
     NewFPFeatures.setAllowFPContractAcrossStatement();
     break;
   case LangOptions::FPM_Off:
     NewFPFeatures.setDisallowFPContract();
     break;
-  case LangOptions::FPM_FastHonorPragmas:
-    llvm_unreachable("Should not happen");
   }
   FpPragmaStack.Act(Loc, Sema::PSK_Set, StringRef(), NewFPFeatures);
   CurFPFeatures = NewFPFeatures.applyOverrides(getLangOpts());
diff --git a/clang/test/CodeGen/ffp-contract-fast-honor-pramga-option.cpp b/clang/test/CodeGen/ffp-contract-fast-honor-pramga-option.cpp
new file mode 100644
index 0000000000000..c2c5daeae6833
--- /dev/null
+++ b/clang/test/CodeGen/ffp-contract-fast-honor-pramga-option.cpp
@@ -0,0 +1,37 @@
+// RUN: %clang_cc1 -O3 -ffp-contract=fast-honor-pragmas -triple %itanium_abi_triple -emit-llvm -o - %s | FileCheck %s
+
+float fp_contract_1(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_1fff(
+  // CHECK: fmul contract float
+  // CHECK: fadd contract float
+  return a * b + c;
+}
+
+float fp_contract_2(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_2fff(
+  // CHECK: fmul contract float
+  // CHECK: fsub contract float
+  return a * b - c;
+}
+
+void fp_contract_3(float *a, float b, float c) {
+  // CHECK-LABEL: fp_contract_3Pfff(
+  // CHECK: fmul contract float
+  // CHECK: fadd contract float
+  a[0] += b * c;
+}
+
+void fp_contract_4(float *a, float b, float c) {
+  // CHECK-LABEL: fp_contract_4Pfff(
+  // CHECK: fmul contract float
+  // CHECK: fsub contract float
+  a[0] -= b * c;
+}
+
+float fp_contract_5(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_5fff(
+  // CHECK: fmul contract float
+  // CHECK: fadd contract float
+  float t = a * b;
+  return t + c;
+}
\ No newline at end of file
diff --git a/clang/test/CodeGen/ffp-contract-fhp-pragma-override.cpp b/clang/test/CodeGen/ffp-contract-fhp-pragma-override.cpp
new file mode 100644
index 0000000000000..15d546b71abbe
--- /dev/null
+++ b/clang/test/CodeGen/ffp-contract-fhp-pragma-override.cpp
@@ -0,0 +1,151 @@
+// RUN: %clang_cc1 -O3 -ffp-contract=fast-honor-pragmas -triple %itanium_abi_triple -emit-llvm -o - %s | FileCheck %s
+
+float fp_contract_on_1(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_on_1fff(
+  // CHECK: call float @llvm.fmuladd.f32(float {{.*}}, float {{.*}}, float {{.*}})
+  #pragma STDC FP_CONTRACT ON
+  return a * b + c;
+}
+
+float fp_contract_on_2(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_on_2fff(
+  // CHECK: fmul float
+  // CHECK: fadd float
+  #pragma STDC FP_CONTRACT ON
+  float t = a * b;
+  return t + c;
+}
+
+float fp_contract_off_1(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_off_1fff(
+  // CHECK: fmul float
+  // CHECK: fadd float
+  #pragma STDC FP_CONTRACT OFF
+  return a * b + c;
+}
+
+float fp_contract_off_2(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_off_2fff(
+  // CHECK: fmul float
+  // CHECK: fadd float
+  #pragma STDC FP_CONTRACT OFF
+  float t = a * b;
+  return t + c;
+}
+
+float fp_contract_default_1(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_default_1fff(
+  // CHECK: fmul contract float
+  // CHECK: fadd contract float
+  #pragma STDC FP_CONTRACT DEFAULT
+  return a * b + c;
+}
+
+float fp_contract_default_2(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_default_2fff(
+  // CHECK: fmul contract float
+  // CHECK: fadd contract float
+  #pragma STDC FP_CONTRACT DEFAULT
+  float t = a * b;
+  return t + c;
+}
+
+float fp_contract_clang_on_1(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_clang_on_1fff(
+  // CHECK: call float @llvm.fmuladd.f32(float {{.*}}, float {{.*}}, float {{.*}})
+  #pragma clang fp contract(on)
+  return a * b + c;
+}
+
+float fp_contract_clang_on_2(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_clang_on_2fff(
+  // CHECK: fmul float
+  // CHECK: fadd float
+  #pragma clang fp contract(on)
+  float t = a * b;
+  return t + c;
+}
+
+float fp_contract_clang_off_1(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_clang_off_1fff(
+  // CHECK: fmul float
+  // CHECK: fadd float
+  #pragma clang fp contract(off)
+  return a * b + c;
+}
+
+float fp_contract_clang_off_2(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_clang_off_2fff(
+  // CHECK: fmul float
+  // CHECK: fadd float
+  #pragma clang fp contract(off)
+  float t = a * b;
+  return t + c;
+}
+
+float fp_contract_clang_fast_1(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_clang_fast_1fff(
+  // CHECK: fmul contract float
+  // CHECK: fadd contract float
+  #pragma clang fp contract(fast)
+  return a * b + c;
+}
+
+float fp_contract_clang_fast_2(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_clang_fast_2fff(
+  // CHECK: fmul contract float
+  // CHECK: fadd contract float
+  #pragma clang fp contract(fast)
+  float t = a * b;
+  return t + c;
+}
+
+#pragma STDC FP_CONTRACT ON
+
+float fp_contract_global_on_1(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_global_on_1fff(
+  // CHECK: call float @llvm.fmuladd.f32(float {{.*}}, float {{.*}}, float {{.*}})
+  return a * b + c;
+}
+
+float fp_contract_global_on_2(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_global_on_2fff(
+  // CHECK: fmul float
+  // CHECK: fadd float
+  float t = a * b;
+  return t + c;
+}
+
+#pragma STDC FP_CONTRACT OFF
+
+float fp_contract_global_off_1(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_global_off_1fff(
+  // CHECK: fmul float
+  // CHECK: fadd float
+  return a * b + c;
+}
+
+float fp_contract_global_off_2(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_global_off_2fff(
+  // CHECK: fmul float
+  // CHECK: fadd float
+  float t = a * b;
+  return t + c;
+}
+
+#pragma STDC FP_CONTRACT DEFAULT
+
+float fp_contract_global_default_1(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_global_default_1fff(
+  // CHECK: fmul contract float
+  // CHECK: fadd contract float
+  return a * b + c;
+}
+
+float fp_contract_global_default_2(float a, float b, float c) {
+  // CHECK-LABEL: fp_contract_global_default_2fff(
+  // CHECK: fmul contract float
+  // CHECK: fadd contract float
+  float t = a * b;
+  return t + c;
+}
\ No newline at end of file

``````````

</details>


https://github.com/llvm/llvm-project/pull/104857