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[SVE] Add folds for truncation of vscale 

Reviewed By: david-arm

Differential Revision: https://reviews.llvm.org/D107453
This commit is contained in:
Dylan Fleming 2021-08-13 09:36:31 +01:00
parent 46abd1fbe8
commit 4be7fb9762
2 changed files with 54 additions and 0 deletions
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14
llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
View File

@ -961,6 +961,20 @@ Instruction *InstCombinerImpl::visitTrunc(TruncInst &Trunc) {
return BinaryOperator::CreateAdd(NarrowCtlz, WidthDiff);
}
}
if (match(Src, m_VScale(DL))) {
if (Trunc.getFunction()->hasFnAttribute(Attribute::VScaleRange)) {
unsigned MaxVScale = Trunc.getFunction()
->getFnAttribute(Attribute::VScaleRange)
.getVScaleRangeArgs()
.second;
if (MaxVScale > 0 && Log2_32(MaxVScale) < DestWidth) {
Value *VScale = Builder.CreateVScale(ConstantInt::get(DestTy, 1));
return replaceInstUsesWith(Trunc, VScale);
}
}
}
return nullptr;
}

40
llvm/test/Transforms/InstCombine/vscale_trunc.ll Normal file
View File

@ -0,0 +1,40 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -instcombine -S | FileCheck %s
define i8 @vscale_trunc_i32toi8() vscale_range(0, 255) {
; CHECK-LABEL: @vscale_trunc_i32toi8(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = call i8 @llvm.vscale.i8()
; CHECK-NEXT: ret i8 [[TMP0]]
entry:
%0 = call i32 @llvm.vscale.i32()
%1 = trunc i32 %0 to i8
ret i8 %1
}
define i8 @vscale_trunc_i32toi8_poison() vscale_range(0, 256) {
; CHECK-LABEL: @vscale_trunc_i32toi8_poison(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = call i32 @llvm.vscale.i32()
; CHECK-NEXT: [[TMP1:%.*]] = trunc i32 [[TMP0]] to i8
; CHECK-NEXT: ret i8 [[TMP1]]
entry:
%0 = call i32 @llvm.vscale.i32()
%1 = trunc i32 %0 to i8
ret i8 %1
}
define i8 @vscale_trunc_i32toi8_noAttr() {
; CHECK-LABEL: @vscale_trunc_i32toi8_noAttr(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = call i32 @llvm.vscale.i32()
; CHECK-NEXT: [[TMP1:%.*]] = trunc i32 [[TMP0]] to i8
; CHECK-NEXT: ret i8 [[TMP1]]
entry:
%0 = call i32 @llvm.vscale.i32()
%1 = trunc i32 %0 to i8
ret i8 %1
}
declare i32 @llvm.vscale.i32()