[PATCH] D21668: [ARM] Fix cost computation for constant hoisting

[Weiming Zhao via llvm-commits]

weimingz set the repository for this revision to rL LLVM.
weimingz updated this revision to Diff 61931.
weimingz added a comment.

Hi Renato,

Thanks for the feedback.
I Simplified the test case and added comments.


Repository:
  rL LLVM

http://reviews.llvm.org/D21668

Files:
  lib/Target/ARM/ARMTargetTransformInfo.cpp
  test/Transforms/ConstantHoisting/ARM/bad-cases.ll

Index: test/Transforms/ConstantHoisting/ARM/bad-cases.ll
===================================================================
--- test/Transforms/ConstantHoisting/ARM/bad-cases.ll
+++ test/Transforms/ConstantHoisting/ARM/bad-cases.ll
@@ -90,3 +90,20 @@
 end:
   ret void
 }
+
+;PR 28282: even when data type is larger than 64-bit, the bit width of the
+;constant operand could be smaller than 64-bit. In this case, there is no
+;benefit to hoist the constant.
+define i32 @struct_type_test(i96 %a0, i96 %a1) {
+;CHECK-LABEL: @struct_type_test
+entry:
+;CHECK-NOT: %const = bitcast i96 32 to i96
+;CHECK: lshr0 = lshr i96 %a0, 32
+  %lshr0 = lshr i96 %a0, 32
+  %cast0 = trunc i96 %lshr0 to i32
+;CHECK: lshr1 = lshr i96 %a1, 32
+  %lshr1 = lshr i96 %a1, 32
+  %cast1 = trunc i96 %lshr1 to i32
+  %ret = add i32 %cast0, %cast1
+  ret i32 %ret
+}
Index: lib/Target/ARM/ARMTargetTransformInfo.cpp
===================================================================
--- lib/Target/ARM/ARMTargetTransformInfo.cpp
+++ lib/Target/ARM/ARMTargetTransformInfo.cpp
@@ -19,7 +19,7 @@
   assert(Ty->isIntegerTy());
 
  unsigned Bits = Ty->getPrimitiveSizeInBits();
- if (Bits == 0 || Bits > 64)
+ if (Bits == 0 || Imm.getActiveBits() >= 64)
    return 4;
 
   int64_t SImmVal = Imm.getSExtValue();


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