[llvm] 8a836da - [InstCombine] Support lshr(trunc(lshr(x, c1)), c2) -> trunc(lshr(lshr(x,c1),c2)) uniform vector tests

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2020-10-09T16:54:46+01:00
New Revision: 8a836daaa97bc979cd589f5efb060d2223225d8d

URL: https://github.com/llvm/llvm-project/commit/8a836daaa97bc979cd589f5efb060d2223225d8d
DIFF: https://github.com/llvm/llvm-project/commit/8a836daaa97bc979cd589f5efb060d2223225d8d.diff

LOG: [InstCombine] Support lshr(trunc(lshr(x,c1)), c2) -> trunc(lshr(lshr(x,c1),c2)) uniform vector tests

FoldShiftByConstant is hardcoded for scalar/uniform outer shift amounts atm so that needs to be fixed first to support non-uniform cases

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
    llvm/test/Transforms/InstCombine/shift.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
index 627e3390ea14..43b700572826 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
@@ -691,8 +691,9 @@ Instruction *InstCombinerImpl::FoldShiftByConstant(Value *Op0, Constant *Op1,
     // require that the input operand is a shift-by-constant so that we have
     // confidence that the shifts will get folded together.  We could do this
     // xform in more cases, but it is unlikely to be profitable.
+    const APInt *TrShiftAmt;
     if (I.isLogicalShift() &&
-        match(TI->getOperand(0), m_Shift(m_Value(), m_ConstantInt()))) {
+        match(TI->getOperand(0), m_Shift(m_Value(), m_APInt(TrShiftAmt)))) {
       auto *TrOp = cast<Instruction>(TI->getOperand(0));
       Type *SrcTy = TrOp->getType();
 

diff  --git a/llvm/test/Transforms/InstCombine/shift.ll b/llvm/test/Transforms/InstCombine/shift.ll
index aca47336fc80..146440862cc4 100644
--- a/llvm/test/Transforms/InstCombine/shift.ll
+++ b/llvm/test/Transforms/InstCombine/shift.ll
@@ -465,9 +465,8 @@ entry:
 define <2 x i32> @test29_uniform(<2 x i64> %d18) {
 ; CHECK-LABEL: @test29_uniform(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[I916:%.*]] = lshr <2 x i64> [[D18:%.*]], <i64 32, i64 32>
-; CHECK-NEXT:    [[I917:%.*]] = trunc <2 x i64> [[I916]] to <2 x i32>
-; CHECK-NEXT:    [[I10:%.*]] = lshr <2 x i32> [[I917]], <i32 31, i32 31>
+; CHECK-NEXT:    [[I916:%.*]] = lshr <2 x i64> [[D18:%.*]], <i64 63, i64 63>
+; CHECK-NEXT:    [[I10:%.*]] = trunc <2 x i64> [[I916]] to <2 x i32>
 ; CHECK-NEXT:    ret <2 x i32> [[I10]]
 ;
 entry: