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[ConstantFold][SVE] Fix constant folding for bitcast.

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Do not iterate on scalable vector type in BitCastConstantVector.
Continuation work of D70985, D71147.

Support for folding bitcast into splat value is kept in D74095, as
it depends on D71637.

Differential Revision: https://reviews.llvm.org/D71389
This commit is contained in:
Huihui Zhang 2020-02-05 11:13:24 -08:00
parent 844565485c
commit 3f01fba31d
2 changed files with 17 additions and 0 deletions
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5
lib/IR/ConstantFold.cpp
View File

@ -47,6 +47,11 @@ static Constant *BitCastConstantVector(Constant *CV, VectorType *DstTy) {
if (CV->isAllOnesValue()) return Constant::getAllOnesValue(DstTy);
if (CV->isNullValue()) return Constant::getNullValue(DstTy);
// Do not iterate on scalable vector. The num of elements is unknown at
// compile-time.
if (DstTy->isScalable())
return nullptr;
// If this cast changes element count then we can't handle it here:
// doing so requires endianness information. This should be handled by
// Analysis/ConstantFolding.cpp

12
test/Analysis/ConstantFolding/bitcast.ll Normal file
View File

@ -0,0 +1,12 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -constprop -S -verify | FileCheck %s
define <vscale x 4 x float> @bitcast_scalable_constant() {
; CHECK-LABEL: @bitcast_scalable_constant(
; CHECK-NEXT: ret <vscale x 4 x float> bitcast (<vscale x 4 x i32> shufflevector (<vscale x 4 x i32> insertelement (<vscale x 4 x i32> undef, i32 1, i32 0), <vscale x 4 x i32> undef, <vscale x 4 x i32> zeroinitializer) to <vscale x 4 x float>)
;
%i1 = insertelement <vscale x 4 x i32> undef, i32 1, i32 0
%i2 = shufflevector <vscale x 4 x i32> %i1, <vscale x 4 x i32> undef, <vscale x 4 x i32> zeroinitializer
%i3 = bitcast <vscale x 4 x i32> %i2 to <vscale x 4 x float>
ret <vscale x 4 x float> %i3
}