[PATCH] D88505: [InstCombine] ease alignment restriction for converting masked load to normal load

[Sanjay Patel via Phabricator via llvm-commits]

spatel created this revision.
spatel added reviewers: lebedev.ri, efriedma, RKSimon.
Herald added subscribers: hiraditya, mcrosier.
Herald added a project: LLVM.
spatel requested review of this revision.

I think we made this fold conservative to be safer, but we do not need the alignment attribute/metadata limitation because the masked load intrinsic itself specifies the alignment. A normal vector load is better for IR transforms and should be no worse in codegen than the masked alternative. If it is worse for some target, the backend can reverse this transform.


https://reviews.llvm.org/D88505

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
  llvm/test/Transforms/InstCombine/masked_intrinsics.ll


Index: llvm/test/Transforms/InstCombine/masked_intrinsics.ll
===================================================================
--- llvm/test/Transforms/InstCombine/masked_intrinsics.ll
+++ llvm/test/Transforms/InstCombine/masked_intrinsics.ll
@@ -100,8 +100,9 @@
 ; CHECK-LABEL: @load_speculative_less_aligned(
 ; CHECK-NEXT:    [[PTV1:%.*]] = insertelement <2 x double> undef, double [[PT:%.*]], i64 0
 ; CHECK-NEXT:    [[PTV2:%.*]] = shufflevector <2 x double> [[PTV1]], <2 x double> undef, <2 x i32> zeroinitializer
-; CHECK-NEXT:    [[RES:%.*]] = call <2 x double> @llvm.masked.load.v2f64.p0v2f64(<2 x double>* nonnull [[PTR:%.*]], i32 4, <2 x i1> [[MASK:%.*]], <2 x double> [[PTV2]])
-; CHECK-NEXT:    ret <2 x double> [[RES]]
+; CHECK-NEXT:    [[UNMASKEDLOAD:%.*]] = load <2 x double>, <2 x double>* [[PTR:%.*]], align 4
+; CHECK-NEXT:    [[TMP1:%.*]] = select <2 x i1> [[MASK:%.*]], <2 x double> [[UNMASKEDLOAD]], <2 x double> [[PTV2]]
+; CHECK-NEXT:    ret <2 x double> [[TMP1]]
 ;
   %ptv1 = insertelement <2 x double> undef, double %pt, i64 0
   %ptv2 = insertelement <2 x double> %ptv1, double %pt, i64 1
Index: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -289,9 +289,8 @@
 
   // If we can unconditionally load from this address, replace with a
   // load/select idiom. TODO: use DT for context sensitive query
-  if (isDereferenceableAndAlignedPointer(LoadPtr, II.getType(), Alignment,
-                                         II.getModule()->getDataLayout(), &II,
-                                         nullptr)) {
+  if (isDereferenceablePointer(LoadPtr, II.getType(),
+                               II.getModule()->getDataLayout(), &II, nullptr)) {
     Value *LI = Builder.CreateAlignedLoad(II.getType(), LoadPtr, Alignment,
                                          "unmaskedload");
     return Builder.CreateSelect(II.getArgOperand(2), LI, II.getArgOperand(3));


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