[PATCH] D39204: [CodeGen] __builtin_sqrt should map to the compiler's intrinsic sqrt function

[Sanjay Patel via Phabricator via cfe-commits]

spatel created this revision.
Herald added a subscriber: mcrosier.

This patch is intended to answer 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?

I know there are follow-up bugs that still need to be solved (https://reviews.llvm.org/D28335), but I think we should answer this first. Also if this patch is correct, it is enough to produce the hoped-for result in the PR27435 examples because we'll get this IR at -O2:

$ ./clang -O2 27435.c -S -o - -emit-llvm | grep llvm.sqrt

  %2 = call <2 x double> @llvm.sqrt.v2f64(<2 x double> %1)
  %2 = call <4 x float> @llvm.sqrt.v4f32(<4 x float> %1)


https://reviews.llvm.org/D39204

Files:
  lib/CodeGen/CGBuiltin.cpp
  test/CodeGen/builtins.c


Index: test/CodeGen/builtins.c
===================================================================
--- test/CodeGen/builtins.c
+++ test/CodeGen/builtins.c
@@ -318,13 +318,13 @@
   // CHECK: call x86_fp80 @llvm.floor.f80
 
   resf = __builtin_sqrtf(F);
-  // CHECK: call float @sqrtf(
+  // CHECK: call float @llvm.sqrt.f32
 
   resd = __builtin_sqrt(D);
-  // CHECK: call double @sqrt(
+  // CHECK: call double @llvm.sqrt.f64
 
   resld = __builtin_sqrtl(LD);
-  // CHECK: call x86_fp80 @sqrtl(
+  // CHECK: call x86_fp80 @llvm.sqrt.f80
 
   resf = __builtin_truncf(F);
   // CHECK: call float @llvm.trunc.f32
Index: lib/CodeGen/CGBuiltin.cpp
===================================================================
--- lib/CodeGen/CGBuiltin.cpp
+++ lib/CodeGen/CGBuiltin.cpp
@@ -941,6 +941,12 @@
   case Builtin::BI__builtin_roundl: {
     return RValue::get(emitUnaryBuiltin(*this, E, Intrinsic::round));
   }
+
+  case Builtin::BI__builtin_sqrt:
+  case Builtin::BI__builtin_sqrtf:
+  case Builtin::BI__builtin_sqrtl:
+    return RValue::get(emitUnaryBuiltin(*this, E, Intrinsic::sqrt));
+
   case Builtin::BI__builtin_fmin:
   case Builtin::BI__builtin_fminf:
   case Builtin::BI__builtin_fminl: {


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