[FPEnv][Clang][Driver] Disable constrained floating point on targets lacking support.

We currently have strict floating point/constrained floating point enabled
for all targets. Constrained SDAG nodes get converted to the regular ones
before reaching the target layer. In theory this should be fine.

However, the changes are exposed to users through multiple clang options
already in use in the field, and the changes are _completely_ _untested_
on almost all of our targets. Bugs have already been found, like
"https://bugs.llvm.org/show_bug.cgi?id=45274".

This patch disables constrained floating point options in clang everywhere
except X86 and SystemZ. A warning will be printed when this happens.

Differential Revision: https://reviews.llvm.org/D80952

diff --git a/clang/include/clang/Basic/DiagnosticFrontendKinds.td b/clang/include/clang/Basic/DiagnosticFrontendKinds.td
index 83c13e0..db334a7 100644 (file)
--- a/clang/include/clang/Basic/DiagnosticFrontendKinds.td
+++ b/clang/include/clang/Basic/DiagnosticFrontendKinds.td
@@ -37,6 +37,12 @@ def note_fe_backend_plugin: Note<"%0">, BackendInfo;
 def warn_fe_override_module : Warning<
     "overriding the module target triple with %0">,
     InGroup<DiagGroup<"override-module">>;
+def warn_fe_backend_unsupported_fp_rounding : Warning<
+    "overriding currently unsupported rounding mode on this target">,
+    InGroup<UnsupportedFPOpt>;
+def warn_fe_backend_unsupported_fp_exceptions : Warning<
+    "overriding currently unsupported use of floating point exceptions "
+    "on this target">, InGroup<UnsupportedFPOpt>;
 
 def remark_fe_backend_optimization_remark : Remark<"%0">, BackendInfo,
     InGroup<BackendOptimizationRemark>;

diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index 37e0b77..ff07608 100644 (file)
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -107,6 +107,7 @@ def DoublePromotion : DiagGroup<"double-promotion">;
 def EnumTooLarge : DiagGroup<"enum-too-large">;
 def UnsupportedNan : DiagGroup<"unsupported-nan">;
 def UnsupportedAbs : DiagGroup<"unsupported-abs">;
+def UnsupportedFPOpt : DiagGroup<"unsupported-floating-point-opt">;
 def UnsupportedCB : DiagGroup<"unsupported-cb">;
 def UnsupportedGPOpt : DiagGroup<"unsupported-gpopt">;
 def UnsupportedTargetOpt : DiagGroup<"unsupported-target-opt">;

diff --git a/clang/include/clang/Basic/TargetInfo.h b/clang/include/clang/Basic/TargetInfo.h
index 140f55f..2ee3b16 100644 (file)
--- a/clang/include/clang/Basic/TargetInfo.h
+++ b/clang/include/clang/Basic/TargetInfo.h
@@ -192,6 +192,7 @@ protected:
   bool HasFloat128;
   bool HasFloat16;
   bool HasBFloat16;
+  bool HasStrictFP;
 
   unsigned char MaxAtomicPromoteWidth, MaxAtomicInlineWidth;
   unsigned short SimdDefaultAlign;
@@ -577,6 +578,9 @@ public:
   /// Determine whether the _BFloat16 type is supported on this target.
   virtual bool hasBFloat16Type() const { return HasBFloat16; }
 
+  /// Determine whether constrained floating point is supported on this target.
+  virtual bool hasStrictFP() const { return HasStrictFP; }
+
   /// Return the alignment that is suitable for storing any
   /// object with a fundamental alignment requirement.
   unsigned getSuitableAlign() const { return SuitableAlign; }

diff --git a/clang/lib/Basic/TargetInfo.cpp b/clang/lib/Basic/TargetInfo.cpp
index 7f360b7..eccdc21 100644 (file)
--- a/clang/lib/Basic/TargetInfo.cpp
+++ b/clang/lib/Basic/TargetInfo.cpp
@@ -37,6 +37,7 @@ TargetInfo::TargetInfo(const llvm::Triple &T) : TargetOpts(), Triple(T) {
   HasFloat128 = false;
   HasFloat16 = false;
   HasBFloat16 = false;
+  HasStrictFP = false;
   PointerWidth = PointerAlign = 32;
   BoolWidth = BoolAlign = 8;
   IntWidth = IntAlign = 32;

diff --git a/clang/lib/Basic/Targets/SystemZ.h b/clang/lib/Basic/Targets/SystemZ.h
index 134b031..d7869e3 100644 (file)
--- a/clang/lib/Basic/Targets/SystemZ.h
+++ b/clang/lib/Basic/Targets/SystemZ.h
@@ -48,6 +48,7 @@ public:
     MinGlobalAlign = 16;
     resetDataLayout("E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-a:8:16-n32:64");
     MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 64;
+    HasStrictFP = true;
   }
 
   void getTargetDefines(const LangOptions &Opts,

diff --git a/clang/lib/Basic/Targets/X86.h b/clang/lib/Basic/Targets/X86.h
index c33c608..d6c9b3f 100644 (file)
--- a/clang/lib/Basic/Targets/X86.h
+++ b/clang/lib/Basic/Targets/X86.h
@@ -138,6 +138,7 @@ public:
       : TargetInfo(Triple) {
     LongDoubleFormat = &llvm::APFloat::x87DoubleExtended();
     AddrSpaceMap = &X86AddrSpaceMap;
+    HasStrictFP = true;
   }
 
   const char *getLongDoubleMangling() const override {

diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index 9dc9c42..189a030 100644 (file)
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -933,6 +933,19 @@ bool CompilerInstance::ExecuteAction(FrontendAction &Act) {
     setAuxTarget(TargetInfo::CreateTargetInfo(getDiagnostics(), TO));
   }
 
+  if (!getTarget().hasStrictFP()) {
+    if (getLangOpts().getFPRoundingMode() !=
+        llvm::RoundingMode::NearestTiesToEven) {
+      getDiagnostics().Report(diag::warn_fe_backend_unsupported_fp_rounding);
+      getLangOpts().setFPRoundingMode(llvm::RoundingMode::NearestTiesToEven);
+    }
+    if (getLangOpts().getFPExceptionMode() != LangOptions::FPE_Ignore) {
+      getDiagnostics().Report(diag::warn_fe_backend_unsupported_fp_exceptions);
+      getLangOpts().setFPExceptionMode(LangOptions::FPE_Ignore);
+    }
+    // FIXME: can we disable FEnvAccess?
+  }
+
   // Inform the target of the language options.
   //
   // FIXME: We shouldn't need to do this, the target should be immutable once

diff --git a/clang/test/CodeGen/aarch64-neon-misc-constrained.c b/clang/test/CodeGen/aarch64-neon-misc-constrained.c
index 0385358..db4474e 100644 (file)
--- a/clang/test/CodeGen/aarch64-neon-misc-constrained.c
+++ b/clang/test/CodeGen/aarch64-neon-misc-constrained.c
@@ -15,6 +15,9 @@
 
 // REQUIRES: aarch64-registered-target
 
+// Disabled until constrained floating point is implemented for arm64.
+// XFAIL: *
+
 // Test new aarch64 intrinsics and types but constrained
 
 #include <arm_neon.h>

diff --git a/clang/test/CodeGen/aarch64-neon-scalar-x-indexed-elem-constrained.c b/clang/test/CodeGen/aarch64-neon-scalar-x-indexed-elem-constrained.c
index cbe5627..c6fa81e 100644 (file)
--- a/clang/test/CodeGen/aarch64-neon-scalar-x-indexed-elem-constrained.c
+++ b/clang/test/CodeGen/aarch64-neon-scalar-x-indexed-elem-constrained.c
@@ -15,6 +15,9 @@
 
 // REQUIRES: aarch64-registered-target
 
+// Disabled until constrained floating point is implemented for arm64.
+// XFAIL: *
+
 // Test new aarch64 intrinsics and types but constrained
 
 #include <arm_neon.h>

diff --git a/clang/test/CodeGen/aarch64-v8.2a-neon-intrinsics-constrained.c b/clang/test/CodeGen/aarch64-v8.2a-neon-intrinsics-constrained.c
index 6058e6f..dd3e92d 100644 (file)
--- a/clang/test/CodeGen/aarch64-v8.2a-neon-intrinsics-constrained.c
+++ b/clang/test/CodeGen/aarch64-v8.2a-neon-intrinsics-constrained.c
@@ -19,6 +19,9 @@
 
 // REQUIRES: aarch64-registered-target
 
+// Disabled until constrained floating point is implemented for arm64.
+// XFAIL: *
+
 #include <arm_neon.h>
 
 // COMMON-LABEL: test_vsqrt_f16

diff --git a/clang/test/CodeGen/arm-neon-directed-rounding-constrained.c b/clang/test/CodeGen/arm-neon-directed-rounding-constrained.c
index 5246993..493f792 100644 (file)
--- a/clang/test/CodeGen/arm-neon-directed-rounding-constrained.c
+++ b/clang/test/CodeGen/arm-neon-directed-rounding-constrained.c
@@ -32,6 +32,9 @@
 
 // REQUIRES: arm-registered-target,aarch64-registered-target
 
+// Disabled until constrained floating point is implemented for arm64.
+// XFAIL: *
+
 #include <arm_neon.h>
 
 // COMMON-LABEL: test_vrndi_f32

diff --git a/clang/test/CodeGen/arm64-vrnd-constrained.c b/clang/test/CodeGen/arm64-vrnd-constrained.c
index bbded8f..f46b1ab 100644 (file)
--- a/clang/test/CodeGen/arm64-vrnd-constrained.c
+++ b/clang/test/CodeGen/arm64-vrnd-constrained.c
@@ -9,6 +9,9 @@
 
 // REQUIRES: aarch64-registered-target
 
+// Disabled until constrained floating point is implemented for arm64.
+// XFAIL: *
+
 #include <arm_neon.h>
 
 float64x2_t rnd5(float64x2_t a) { return vrndq_f64(a); }

diff --git a/clang/test/CodeGen/builtins-ppc-fpconstrained.c b/clang/test/CodeGen/builtins-ppc-fpconstrained.c
index 38cdfb6..1e6da68 100644 (file)
--- a/clang/test/CodeGen/builtins-ppc-fpconstrained.c
+++ b/clang/test/CodeGen/builtins-ppc-fpconstrained.c
@@ -12,6 +12,9 @@
 // RUN: -o - %s | FileCheck --check-prefix=CHECK-ASM \
 // RUN: --check-prefix=FIXME-CHECK  %s
 
+// Disabled until constrained floating point is completed for PowerPC.
+// XFAIL: *
+
 typedef __attribute__((vector_size(4 * sizeof(float)))) float vec_float;
 typedef __attribute__((vector_size(2 * sizeof(double)))) double vec_double;
 

diff --git a/clang/test/CodeGen/fp-strictfp.cpp b/clang/test/CodeGen/fp-strictfp.cpp
new file mode 100644 (file)
index 0000000..1a88a54
--- /dev/null
+++ b/clang/test/CodeGen/fp-strictfp.cpp
@@ -0,0 +1,18 @@
+// RUN: %clang_cc1 -triple mips64-linux-gnu -frounding-math -ffp-exception-behavior=strict -O2 -verify=rounding,exception -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -triple mips64-linux-gnu -ffp-exception-behavior=strict -O2 -verify=exception -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -triple mips64-linux-gnu -frounding-math -O2 -verify=rounding -emit-llvm -o - %s | FileCheck %s
+//
+// Verify that constrained intrinsics are not used.
+// As more targets gain support for constrained intrinsics the triple
+// in this test will need to change.
+
+// rounding-warning@* {{overriding currently unsupported rounding mode on this target}}
+// exception-warning@* {{overriding currently unsupported use of floating point exceptions on this target}}
+float fp_precise_1(float a, float b, float c) {
+// CHECK: _Z12fp_precise_1fff
+// CHECK: %[[M:.+]] = fmul float{{.*}}
+// CHECK: fadd float %[[M]], %c
+  return a * b + c;
+}
+
+