[llvm] r343407 - [InstCombine] try to convert vector insert+extract to trunc
Hans Wennborg via llvm-commits
llvm-commits at lists.llvm.org
Mon Oct 1 05:09:56 PDT 2018
I've reverted in r343458 as it caused assertions while building Chromium.
The repro is available here:
https://bugs.chromium.org/p/chromium/issues/detail?id=890723#c1
On Sun, Sep 30, 2018 at 4:34 PM, Sanjay Patel via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: spatel
> Date: Sun Sep 30 07:34:01 2018
> New Revision: 343407
>
> URL: http://llvm.org/viewvc/llvm-project?rev=343407&view=rev
> Log:
> [InstCombine] try to convert vector insert+extract to trunc
>
> This transform is requested for the backend in:
> https://bugs.llvm.org/show_bug.cgi?id=39016
> ...but I figured it was worth doing in IR too, and it's probably
> easier to implement here, so that's this patch.
>
> In the simplest case, we are just truncating a scalar value. If the
> extract index doesn't correspond to the LSBs of the scalar, then we
> have to shift-right before the truncate. Endian-ness makes this tricky,
> but hopefully the ASCII-art helps visualize the transform.
>
> Differential Revision: https://reviews.llvm.org/D52439
>
> Modified:
> llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
> llvm/trunk/test/Transforms/InstCombine/extractelement.ll
>
> Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp?rev=343407&r1=343406&r2=343407&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp (original)
> +++ llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp Sun Sep 30 07:34:01 2018
> @@ -167,7 +167,8 @@ Instruction *InstCombiner::scalarizePHI(
> }
>
> static Instruction *foldBitcastExtElt(ExtractElementInst &Ext,
> - InstCombiner::BuilderTy &Builder) {
> + InstCombiner::BuilderTy &Builder,
> + bool IsBigEndian) {
> Value *X;
> uint64_t ExtIndexC;
> if (!match(Ext.getVectorOperand(), m_BitCast(m_Value(X))) ||
> @@ -186,6 +187,47 @@ static Instruction *foldBitcastExtElt(Ex
> if (Value *Elt = findScalarElement(X, ExtIndexC))
> return new BitCastInst(Elt, DestTy);
>
> + // If the source elements are wider than the destination, try to shift and
> + // truncate a subset of scalar bits of an insert op.
> + if (NumSrcElts < NumElts && SrcTy->getScalarType()->isIntegerTy()) {
> + Value *Scalar;
> + uint64_t InsIndexC;
> + if (!match(X, m_InsertElement(m_Value(), m_Value(Scalar),
> + m_ConstantInt(InsIndexC))))
> + return nullptr;
> +
> + // The extract must be from the subset of vector elements that we inserted
> + // into. Example: if we inserted element 1 of a <2 x i64> and we are
> + // extracting an i16 (narrowing ratio = 4), then this extract must be from 1
> + // of elements 4-7 of the bitcasted vector.
> + unsigned NarrowingRatio = NumElts / NumSrcElts;
> + if (ExtIndexC / NarrowingRatio != InsIndexC)
> + return nullptr;
> +
> + // We are extracting part of the original scalar. How that scalar is
> + // inserted into the vector depends on the endian-ness. Example:
> + // Vector Byte Elt Index: 0 1 2 3 4 5 6 7
> + // +--+--+--+--+--+--+--+--+
> + // inselt <2 x i32> V, <i32> S, 1: |V0|V1|V2|V3|S0|S1|S2|S3|
> + // extelt <4 x i16> V', 3: | |S2|S3|
> + // +--+--+--+--+--+--+--+--+
> + // If this is little-endian, S2|S3 are the MSB of the 32-bit 'S' value.
> + // If this is big-endian, S2|S3 are the LSB of the 32-bit 'S' value.
> + // In this example, we must right-shift little-endian. Big-endian is just a
> + // truncate.
> + unsigned Chunk = ExtIndexC % NarrowingRatio;
> + if (IsBigEndian)
> + Chunk = NarrowingRatio - 1 - Chunk;
> + unsigned ShAmt = Chunk * DestTy->getPrimitiveSizeInBits();
> + if (ShAmt) {
> + // Bail out if we could end with more instructions than we started with.
> + if (!Ext.getVectorOperand()->hasOneUse())
> + return nullptr;
> + Scalar = Builder.CreateLShr(Scalar, ShAmt);
> + }
> + return new TruncInst(Scalar, DestTy);
> + }
> +
> return nullptr;
> }
>
> @@ -224,7 +266,7 @@ Instruction *InstCombiner::visitExtractE
> }
> }
>
> - if (Instruction *I = foldBitcastExtElt(EI, Builder))
> + if (Instruction *I = foldBitcastExtElt(EI, Builder, DL.isBigEndian()))
> return I;
>
> // If there's a vector PHI feeding a scalar use through this extractelement
>
> Modified: llvm/trunk/test/Transforms/InstCombine/extractelement.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/extractelement.ll?rev=343407&r1=343406&r2=343407&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/InstCombine/extractelement.ll (original)
> +++ llvm/trunk/test/Transforms/InstCombine/extractelement.ll Sun Sep 30 07:34:01 2018
> @@ -42,11 +42,14 @@ define i64 @test2(i64 %in) {
> }
>
> define i32 @bitcasted_inselt_wide_source_zero_elt(i64 %x) {
> -; ANY-LABEL: @bitcasted_inselt_wide_source_zero_elt(
> -; ANY-NEXT: [[I:%.*]] = insertelement <2 x i64> undef, i64 [[X:%.*]], i32 0
> -; ANY-NEXT: [[B:%.*]] = bitcast <2 x i64> [[I]] to <4 x i32>
> -; ANY-NEXT: [[R:%.*]] = extractelement <4 x i32> [[B]], i32 0
> -; ANY-NEXT: ret i32 [[R]]
> +; LE-LABEL: @bitcasted_inselt_wide_source_zero_elt(
> +; LE-NEXT: [[R:%.*]] = trunc i64 [[X:%.*]] to i32
> +; LE-NEXT: ret i32 [[R]]
> +;
> +; BE-LABEL: @bitcasted_inselt_wide_source_zero_elt(
> +; BE-NEXT: [[TMP1:%.*]] = lshr i64 [[X:%.*]], 32
> +; BE-NEXT: [[R:%.*]] = trunc i64 [[TMP1]] to i32
> +; BE-NEXT: ret i32 [[R]]
> ;
> %i = insertelement <2 x i64> zeroinitializer, i64 %x, i32 0
> %b = bitcast <2 x i64> %i to <4 x i32>
> @@ -55,11 +58,14 @@ define i32 @bitcasted_inselt_wide_source
> }
>
> define i16 @bitcasted_inselt_wide_source_modulo_elt(i64 %x) {
> -; ANY-LABEL: @bitcasted_inselt_wide_source_modulo_elt(
> -; ANY-NEXT: [[I:%.*]] = insertelement <2 x i64> undef, i64 [[X:%.*]], i32 1
> -; ANY-NEXT: [[B:%.*]] = bitcast <2 x i64> [[I]] to <8 x i16>
> -; ANY-NEXT: [[R:%.*]] = extractelement <8 x i16> [[B]], i32 4
> -; ANY-NEXT: ret i16 [[R]]
> +; LE-LABEL: @bitcasted_inselt_wide_source_modulo_elt(
> +; LE-NEXT: [[R:%.*]] = trunc i64 [[X:%.*]] to i16
> +; LE-NEXT: ret i16 [[R]]
> +;
> +; BE-LABEL: @bitcasted_inselt_wide_source_modulo_elt(
> +; BE-NEXT: [[TMP1:%.*]] = lshr i64 [[X:%.*]], 48
> +; BE-NEXT: [[R:%.*]] = trunc i64 [[TMP1]] to i16
> +; BE-NEXT: ret i16 [[R]]
> ;
> %i = insertelement <2 x i64> undef, i64 %x, i32 1
> %b = bitcast <2 x i64> %i to <8 x i16>
> @@ -68,11 +74,14 @@ define i16 @bitcasted_inselt_wide_source
> }
>
> define i32 @bitcasted_inselt_wide_source_not_modulo_elt(i64 %x) {
> -; ANY-LABEL: @bitcasted_inselt_wide_source_not_modulo_elt(
> -; ANY-NEXT: [[I:%.*]] = insertelement <2 x i64> undef, i64 [[X:%.*]], i32 0
> -; ANY-NEXT: [[B:%.*]] = bitcast <2 x i64> [[I]] to <4 x i32>
> -; ANY-NEXT: [[R:%.*]] = extractelement <4 x i32> [[B]], i32 1
> -; ANY-NEXT: ret i32 [[R]]
> +; LE-LABEL: @bitcasted_inselt_wide_source_not_modulo_elt(
> +; LE-NEXT: [[TMP1:%.*]] = lshr i64 [[X:%.*]], 32
> +; LE-NEXT: [[R:%.*]] = trunc i64 [[TMP1]] to i32
> +; LE-NEXT: ret i32 [[R]]
> +;
> +; BE-LABEL: @bitcasted_inselt_wide_source_not_modulo_elt(
> +; BE-NEXT: [[R:%.*]] = trunc i64 [[X:%.*]] to i32
> +; BE-NEXT: ret i32 [[R]]
> ;
> %i = insertelement <2 x i64> undef, i64 %x, i32 0
> %b = bitcast <2 x i64> %i to <4 x i32>
> @@ -81,11 +90,15 @@ define i32 @bitcasted_inselt_wide_source
> }
>
> define i8 @bitcasted_inselt_wide_source_not_modulo_elt_not_half(i32 %x) {
> -; ANY-LABEL: @bitcasted_inselt_wide_source_not_modulo_elt_not_half(
> -; ANY-NEXT: [[I:%.*]] = insertelement <2 x i32> undef, i32 [[X:%.*]], i32 0
> -; ANY-NEXT: [[B:%.*]] = bitcast <2 x i32> [[I]] to <8 x i8>
> -; ANY-NEXT: [[R:%.*]] = extractelement <8 x i8> [[B]], i32 2
> -; ANY-NEXT: ret i8 [[R]]
> +; LE-LABEL: @bitcasted_inselt_wide_source_not_modulo_elt_not_half(
> +; LE-NEXT: [[TMP1:%.*]] = lshr i32 [[X:%.*]], 16
> +; LE-NEXT: [[R:%.*]] = trunc i32 [[TMP1]] to i8
> +; LE-NEXT: ret i8 [[R]]
> +;
> +; BE-LABEL: @bitcasted_inselt_wide_source_not_modulo_elt_not_half(
> +; BE-NEXT: [[TMP1:%.*]] = lshr i32 [[X:%.*]], 8
> +; BE-NEXT: [[R:%.*]] = trunc i32 [[TMP1]] to i8
> +; BE-NEXT: ret i8 [[R]]
> ;
> %i = insertelement <2 x i32> undef, i32 %x, i32 0
> %b = bitcast <2 x i32> %i to <8 x i8>
> @@ -94,11 +107,15 @@ define i8 @bitcasted_inselt_wide_source_
> }
>
> define i3 @bitcasted_inselt_wide_source_not_modulo_elt_not_half_weird_types(i15 %x) {
> -; ANY-LABEL: @bitcasted_inselt_wide_source_not_modulo_elt_not_half_weird_types(
> -; ANY-NEXT: [[I:%.*]] = insertelement <3 x i15> undef, i15 [[X:%.*]], i32 0
> -; ANY-NEXT: [[B:%.*]] = bitcast <3 x i15> [[I]] to <15 x i3>
> -; ANY-NEXT: [[R:%.*]] = extractelement <15 x i3> [[B]], i32 1
> -; ANY-NEXT: ret i3 [[R]]
> +; LE-LABEL: @bitcasted_inselt_wide_source_not_modulo_elt_not_half_weird_types(
> +; LE-NEXT: [[TMP1:%.*]] = lshr i15 [[X:%.*]], 3
> +; LE-NEXT: [[R:%.*]] = trunc i15 [[TMP1]] to i3
> +; LE-NEXT: ret i3 [[R]]
> +;
> +; BE-LABEL: @bitcasted_inselt_wide_source_not_modulo_elt_not_half_weird_types(
> +; BE-NEXT: [[TMP1:%.*]] = lshr i15 [[X:%.*]], 9
> +; BE-NEXT: [[R:%.*]] = trunc i15 [[TMP1]] to i3
> +; BE-NEXT: ret i3 [[R]]
> ;
> %i = insertelement <3 x i15> undef, i15 %x, i32 0
> %b = bitcast <3 x i15> %i to <15 x i3>
> @@ -125,12 +142,19 @@ define i8 @bitcasted_inselt_wide_source_
> declare void @use(<8 x i8>)
>
> define i8 @bitcasted_inselt_wide_source_uses(i32 %x) {
> -; ANY-LABEL: @bitcasted_inselt_wide_source_uses(
> -; ANY-NEXT: [[I:%.*]] = insertelement <2 x i32> undef, i32 [[X:%.*]], i32 0
> -; ANY-NEXT: [[B:%.*]] = bitcast <2 x i32> [[I]] to <8 x i8>
> -; ANY-NEXT: call void @use(<8 x i8> [[B]])
> -; ANY-NEXT: [[R:%.*]] = extractelement <8 x i8> [[B]], i32 3
> -; ANY-NEXT: ret i8 [[R]]
> +; LE-LABEL: @bitcasted_inselt_wide_source_uses(
> +; LE-NEXT: [[I:%.*]] = insertelement <2 x i32> undef, i32 [[X:%.*]], i32 0
> +; LE-NEXT: [[B:%.*]] = bitcast <2 x i32> [[I]] to <8 x i8>
> +; LE-NEXT: call void @use(<8 x i8> [[B]])
> +; LE-NEXT: [[R:%.*]] = extractelement <8 x i8> [[B]], i32 3
> +; LE-NEXT: ret i8 [[R]]
> +;
> +; BE-LABEL: @bitcasted_inselt_wide_source_uses(
> +; BE-NEXT: [[I:%.*]] = insertelement <2 x i32> undef, i32 [[X:%.*]], i32 0
> +; BE-NEXT: [[B:%.*]] = bitcast <2 x i32> [[I]] to <8 x i8>
> +; BE-NEXT: call void @use(<8 x i8> [[B]])
> +; BE-NEXT: [[R:%.*]] = trunc i32 [[X]] to i8
> +; BE-NEXT: ret i8 [[R]]
> ;
> %i = insertelement <2 x i32> undef, i32 %x, i32 0
> %b = bitcast <2 x i32> %i to <8 x i8>
>
>
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
More information about the llvm-commits
mailing list