[PATCH] D34699: [InstCombine] Propagate nsw flag when turning mul by pow2 into shift when the constant is a vector splat or the scalar bit width is larger than 64-bits

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.

The check to see if we can propagate the nsw flag used m_ConstantInt(uint64_t*&) which doesn't work with splat vectors and has a restriction that the bitwidth of the ConstantInt must be 64-bits are less.

This patch changes it to use m_APInt to remove both these issues.


https://reviews.llvm.org/D34699

Files:
  lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
  test/Transforms/InstCombine/mul.ll


Index: test/Transforms/InstCombine/mul.ll
===================================================================
--- test/Transforms/InstCombine/mul.ll
+++ test/Transforms/InstCombine/mul.ll
@@ -300,7 +300,7 @@
 
 define <2 x i32> @test32vec(<2 x i32> %X) {
 ; CHECK-LABEL: @test32vec(
-; CHECK-NEXT:    [[MUL:%.*]] = shl <2 x i32> [[X:%.*]], <i32 31, i32 31>
+; CHECK-NEXT:    [[MUL:%.*]] = shl nsw <2 x i32> [[X:%.*]], <i32 31, i32 31>
 ; CHECK-NEXT:    ret <2 x i32> [[MUL]]
 ;
   %mul = mul nsw <2 x i32> %X, <i32 -2147483648, i32 -2147483648>
@@ -315,20 +315,18 @@
   ret i32 %mul
 }
 
-; TODO: we should propagate nsw flag to the shift here
 define <2 x i32> @test33vec(<2 x i32> %X) {
 ; CHECK-LABEL: @test33vec(
-; CHECK-NEXT:    [[MUL:%.*]] = shl <2 x i32> [[X:%.*]], <i32 30, i32 30>
+; CHECK-NEXT:    [[MUL:%.*]] = shl nsw <2 x i32> [[X:%.*]], <i32 30, i32 30>
 ; CHECK-NEXT:    ret <2 x i32> [[MUL]]
 ;
   %mul = mul nsw <2 x i32> %X, <i32 1073741824, i32 1073741824>
   ret <2 x i32> %mul
 }
 
-; TODO: we should propagate nsw flag to the shift here, but we only handle i64 and smaller
 define i128 @test34(i128 %X) {
 ; CHECK-LABEL: @test34(
-; CHECK-NEXT:    [[MUL:%.*]] = shl i128 [[X:%.*]], 1
+; CHECK-NEXT:    [[MUL:%.*]] = shl nsw i128 [[X:%.*]], 1
 ; CHECK-NEXT:    ret i128 [[MUL]]
 ;
   %mul = mul nsw i128 %X, 2
Index: lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -227,8 +227,8 @@
         if (I.hasNoUnsignedWrap())
           Shl->setHasNoUnsignedWrap();
         if (I.hasNoSignedWrap()) {
-          uint64_t V;
-          if (match(NewCst, m_ConstantInt(V)) && V != Width - 1)
+          const APInt *V;
+          if (match(NewCst, m_APInt(V)) && *V != Width - 1)
             Shl->setHasNoSignedWrap();
         }
 


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