[CodeGen] map sqrt libcalls to llvm.sqrt when errno is not set

The LLVM sqrt intrinsic definition changed with:
D28797
...so we don't have to use any relaxed FP settings other than errno handling.

This patch sidesteps a question raised in PR27435:
https://bugs.llvm.org/show_bug.cgi?id=27435

Is a programmer using __builtin_sqrt() invoking the compiler's intrinsic definition of sqrt or the mathlib definition of sqrt?

But we have an answer now: the builtin should match the behavior of the libm function including errno handling.

Differential Revision: https://reviews.llvm.org/D39204

llvm-svn: 317031

3 files changed, 31 insertions, 23 deletions

diff --git a/clang/test/CodeGen/2005-07-20-SqrtNoErrno.c b/clang/test/CodeGen/2005-07-20-SqrtNoErrno.c
deleted file mode 100644
index 96761e4cfb2..00000000000
--- a/clang/test/CodeGen/2005-07-20-SqrtNoErrno.c
+++ /dev/null
@@ -1,10 +0,0 @@
-// RUN: %clang_cc1 -triple x86_64-apple-darwin %s -emit-llvm -o - | FileCheck %s
-// llvm.sqrt has undefined behavior on negative inputs, so it is
-// inappropriate to translate C/C++ sqrt to this.
-float sqrtf(float x);
-float foo(float X) {
-  // CHECK: foo
-  // CHECK: call float @sqrtf(float %
-  // Check that this is marked readonly when errno is ignored.
-  return sqrtf(X);
-}
diff --git a/clang/test/CodeGen/builtin-sqrt.c b/clang/test/CodeGen/builtin-sqrt.c
new file mode 100644
index 00000000000..f93c5926d5e
--- /dev/null
+++ b/clang/test/CodeGen/builtin-sqrt.c
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -fmath-errno -triple x86_64-apple-darwin %s -emit-llvm -o - | FileCheck %s --check-prefix=HAS_ERRNO
+// RUN: %clang_cc1              -triple x86_64-apple-darwin %s -emit-llvm -o - | FileCheck %s --check-prefix=NO_ERRNO
+
+// FIXME: If a builtin is supposed to have identical semantics to its libm twin, then it
+// should not be marked "constant" in Builtins.def because that means it can't set errno.
+// Note that both runs have 'readnone' on the libcall here.
+
+float foo(float X) {
+  // HAS_ERRNO: call float @sqrtf(float
+  // NO_ERRNO: call float @sqrtf(float
+  return __builtin_sqrtf(X);
+}
+
+// HAS_ERRNO: declare float @sqrtf(float) [[ATTR:#[0-9]+]]
+// HAS_ERRNO: attributes [[ATTR]] = { nounwind readnone {{.*}}}
+
+// NO_ERRNO: declare float @sqrtf(float) [[ATTR:#[0-9]+]]
+// NO_ERRNO: attributes [[ATTR]] = { nounwind readnone {{.*}}}
+
diff --git a/clang/test/CodeGen/libcalls.c b/clang/test/CodeGen/libcalls.c
index 3a8207b2beb..0a1bcc605ca 100644
--- a/clang/test/CodeGen/libcalls.c
+++ b/clang/test/CodeGen/libcalls.c
@@ -6,29 +6,28 @@
 // CHECK-NO-LABEL: define void @test_sqrt
 // CHECK-FAST-LABEL: define void @test_sqrt
 void test_sqrt(float a0, double a1, long double a2) {
-  // Following llvm-gcc's lead, we never emit these as intrinsics;
-  // no-math-errno isn't good enough.  We could probably use intrinsics
-  // with appropriate guards if it proves worthwhile.
-
   // CHECK-YES: call float @sqrtf
-  // CHECK-NO: call float @sqrtf
+  // CHECK-NO: call float @llvm.sqrt.f32(float
+  // CHECK-FAST: call float @llvm.sqrt.f32(float
   float l0 = sqrtf(a0);
 
   // CHECK-YES: call double @sqrt
-  // CHECK-NO: call double @sqrt
+  // CHECK-NO: call double @llvm.sqrt.f64(double
+  // CHECK-FAST: call double @llvm.sqrt.f64(double
   double l1 = sqrt(a1);
 
   // CHECK-YES: call x86_fp80 @sqrtl
-  // CHECK-NO: call x86_fp80 @sqrtl
+  // CHECK-NO: call x86_fp80 @llvm.sqrt.f80(x86_fp80
+  // CHECK-FAST: call x86_fp80 @llvm.sqrt.f80(x86_fp80
   long double l2 = sqrtl(a2);
 }
 
 // CHECK-YES: declare float @sqrtf(float)
 // CHECK-YES: declare double @sqrt(double)
 // CHECK-YES: declare x86_fp80 @sqrtl(x86_fp80)
-// CHECK-NO: declare float @sqrtf(float) [[NUW_RN:#[0-9]+]]
-// CHECK-NO: declare double @sqrt(double) [[NUW_RN]]
-// CHECK-NO: declare x86_fp80 @sqrtl(x86_fp80) [[NUW_RN]]
+// CHECK-NO: declare float @llvm.sqrt.f32(float)
+// CHECK-NO: declare double @llvm.sqrt.f64(double)
+// CHECK-NO: declare x86_fp80 @llvm.sqrt.f80(x86_fp80)
 // CHECK-FAST: declare float @llvm.sqrt.f32(float)
 // CHECK-FAST: declare double @llvm.sqrt.f64(double)
 // CHECK-FAST: declare x86_fp80 @llvm.sqrt.f80(x86_fp80)
@@ -86,7 +85,7 @@ void test_builtins(double d, float f, long double ld) {
   double atan_ = atan(d);
   long double atanl_ = atanl(ld);
   float atanf_ = atanf(f);
-// CHECK-NO: declare double @atan(double) [[NUW_RN]]
+// CHECK-NO: declare double @atan(double) [[NUW_RN:#[0-9]+]]
 // CHECK-NO: declare x86_fp80 @atanl(x86_fp80) [[NUW_RN]]
 // CHECK-NO: declare float @atanf(float) [[NUW_RN]]
 // CHECK-YES-NOT: declare double @atan(double) [[NUW_RN]]
@@ -126,5 +125,5 @@ void test_builtins(double d, float f, long double ld) {
 
 // CHECK-YES: attributes [[NUW_RN]] = { nounwind readnone speculatable }
 
-// CHECK-NO: attributes [[NUW_RN]] = { nounwind readnone{{.*}} }
-// CHECK-NO: attributes [[NUW_RNI]] = { nounwind readnone speculatable }
+// CHECK-NO-DAG: attributes [[NUW_RN]] = { nounwind readnone{{.*}} }
+// CHECK-NO-DAG: attributes [[NUW_RNI]] = { nounwind readnone speculatable }