[llvm] r279970 - [TargetLowering] remove fdiv and frem from canOpTrap() (PR29114)

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Mon Aug 29 08:32:41 2016
New Revision: 279970

URL: http://llvm.org/viewvc/llvm-project?rev=279970&view=rev
Log:
[TargetLowering] remove fdiv and frem from canOpTrap() (PR29114)

Assuming the default FP env, we should not treat fdiv and frem any differently in terms of 
trapping behavior than any other FP op. Ie, FP ops do not trap with the default FP env.

This matches how we treat these ops in IR with isSafeToSpeculativelyExecute(). There's a 
similar bug in Constant::canTrap().

This bug manifests in PR29114:
https://llvm.org/bugs/show_bug.cgi?id=29114
...as a sequence of scalar divisions instead of a vector division on x86 for a <3 x float> 
type.

Differential Revision: https://reviews.llvm.org/D23974

Modified:
    llvm/trunk/include/llvm/Target/TargetLowering.h
    llvm/trunk/lib/CodeGen/TargetLoweringBase.cpp
    llvm/trunk/test/CodeGen/X86/vec3.ll

Modified: llvm/trunk/include/llvm/Target/TargetLowering.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Target/TargetLowering.h?rev=279970&r1=279969&r2=279970&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Target/TargetLowering.h (original)
+++ llvm/trunk/include/llvm/Target/TargetLowering.h Mon Aug 29 08:32:41 2016
@@ -592,7 +592,7 @@ public:
   /// Returns true if the operation can trap for the value type.
   ///
   /// VT must be a legal type. By default, we optimistically assume most
-  /// operations don't trap except for divide and remainder.
+  /// operations don't trap except for integer divide and remainder.
   virtual bool canOpTrap(unsigned Op, EVT VT) const;
 
   /// Similar to isShuffleMaskLegal. This is used by Targets can use this to

Modified: llvm/trunk/lib/CodeGen/TargetLoweringBase.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/TargetLoweringBase.cpp?rev=279970&r1=279969&r2=279970&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/TargetLoweringBase.cpp (original)
+++ llvm/trunk/lib/CodeGen/TargetLoweringBase.cpp Mon Aug 29 08:32:41 2016
@@ -955,15 +955,11 @@ EVT TargetLoweringBase::getShiftAmountTy
   return getScalarShiftAmountTy(DL, LHSTy);
 }
 
-/// canOpTrap - Returns true if the operation can trap for the value type.
-/// VT must be a legal type.
 bool TargetLoweringBase::canOpTrap(unsigned Op, EVT VT) const {
   assert(isTypeLegal(VT));
   switch (Op) {
   default:
     return false;
-  case ISD::FDIV:
-  case ISD::FREM:
   case ISD::SDIV:
   case ISD::UDIV:
   case ISD::SREM:

Modified: llvm/trunk/test/CodeGen/X86/vec3.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/vec3.ll?rev=279970&r1=279969&r2=279970&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/vec3.ll (original)
+++ llvm/trunk/test/CodeGen/X86/vec3.ll Mon Aug 29 08:32:41 2016
@@ -19,16 +19,8 @@ define <3 x float> @fadd(<3 x float> %v,
 define <3 x float> @fdiv(<3 x float> %v, float %d) {
 ; CHECK-LABEL: fdiv:
 ; CHECK:       # BB#0:
-; CHECK-NEXT:    movaps %xmm1, %xmm2
-; CHECK-NEXT:    movaps %xmm0, %xmm3
-; CHECK-NEXT:    movaps %xmm1, %xmm4
-; CHECK-NEXT:    divss %xmm0, %xmm1
-; CHECK-NEXT:    shufps {{.*#+}} xmm0 = xmm0[1,1,2,3]
-; CHECK-NEXT:    divss %xmm0, %xmm2
-; CHECK-NEXT:    movhlps {{.*#+}} xmm3 = xmm3[1,1]
-; CHECK-NEXT:    divss %xmm3, %xmm4
-; CHECK-NEXT:    unpcklps {{.*#+}} xmm1 = xmm1[0],xmm4[0],xmm1[1],xmm4[1]
-; CHECK-NEXT:    unpcklps {{.*#+}} xmm1 = xmm1[0],xmm2[0],xmm1[1],xmm2[1]
+; CHECK-NEXT:    shufps {{.*#+}} xmm1 = xmm1[0,0,0,3]
+; CHECK-NEXT:    divps %xmm0, %xmm1
 ; CHECK-NEXT:    movaps %xmm1, %xmm0
 ; CHECK-NEXT:    retq
 ;