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[ConstantFold] Improve the bitcast folding logic for constant vectors. 

The constant folder didn't know how to always fold bitcasts of constant integer
vectors. In particular, it was unable to handle the case where a constant vector
had some undef elements, and the resulting (i.e. bitcasted) vector type had more
elements than the original vector type.

Example:
  %cast = bitcast <2 x i64><i64 undef, i64 2> to <4 x i32>

On a little endian target, %cast could have been folded to:
  <4 x i32><i32 undef, i32 undef, i32 2, i32 0>

This patch improves the folding logic by teaching how to correctly propagate
undef elements in the folded vector.

Differential Revision: https://reviews.llvm.org/D24301

llvm-svn: 281343
This commit is contained in:
Andrea Di Biagio 2016-09-13 14:50:47 +00:00
parent 161c7f8661
commit 7277afeec1
3 changed files with 35 additions and 25 deletions
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15
llvm/lib/Analysis/ConstantFolding.cpp
View File

@ -224,8 +224,19 @@ Constant *FoldBitCast(Constant *C, Type *DestTy, const DataLayout &DL) {
// Loop over each source value, expanding into multiple results.
for (unsigned i = 0; i != NumSrcElt; ++i) {
auto *Src = dyn_cast_or_null<ConstantInt>(C->getAggregateElement(i));
if (!Src) // Reject constantexpr elements.
auto *Element = C->getAggregateElement(i);
if (!Element) // Reject constantexpr elements.
return ConstantExpr::getBitCast(C, DestTy);
if (isa<UndefValue>(Element)) {
// Correctly Propagate undef values.
Result.append(Ratio, UndefValue::get(DstEltTy));
continue;
}
auto *Src = dyn_cast<ConstantInt>(Element);
if (!Src)
return ConstantExpr::getBitCast(C, DestTy);
unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);

9
llvm/test/Transforms/InstCombine/x86-sse4a.ll
View File

@ -57,8 +57,7 @@ define <2 x i64> @test_extrq_constant_undef(<2 x i64> %x, <16 x i8> %y) {
define <2 x i64> @test_extrq_call_constexpr(<2 x i64> %x) {
; CHECK-LABEL: @test_extrq_call_constexpr(
; CHECK-NEXT: [[TMP1:%.*]] = call <2 x i64> @llvm.x86.sse4a.extrq(<2 x i64> %x, <16 x i8> bitcast (<2 x i64> <i64 0, i64 undef> to <16 x i8>))
; CHECK-NEXT: ret <2 x i64> [[TMP1]]
; CHECK-NEXT: ret <2 x i64> %x
;
%1 = call <2 x i64> @llvm.x86.sse4a.extrq(<2 x i64> %x, <16 x i8> bitcast (<2 x i64> <i64 0, i64 undef> to <16 x i8>))
ret <2 x i64> %1
@ -133,7 +132,7 @@ define <2 x i64> @test_extrqi_constant_undef(<2 x i64> %x) {
define <2 x i64> @test_extrqi_call_constexpr() {
; CHECK-LABEL: @test_extrqi_call_constexpr(
; CHECK-NEXT: ret <2 x i64> bitcast (<16 x i8> <i8 extractelement (<16 x i8> trunc (<16 x i16> bitcast (<4 x i64> <i64 0, i64 undef, i64 2, i64 undef> to <16 x i16>) to <16 x i8>), i32 2), i8 0, i8 0, i8 0, i8 0, i8 0, i8 0, i8 0, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef> to <2 x i64>)
; CHECK-NEXT: ret <2 x i64> zeroinitializer
;
%1 = tail call <2 x i64> @llvm.x86.sse4a.extrqi(<2 x i64> bitcast (<16 x i8> trunc (<16 x i16> bitcast (<4 x i64> <i64 0, i64 undef, i64 2, i64 undef> to <16 x i16>) to <16 x i8>) to <2 x i64>), i8 8, i8 16)
ret <2 x i64> %1
@ -179,7 +178,7 @@ define <2 x i64> @test_insertq_constant_undef(<2 x i64> %x, <2 x i64> %y) {
define <2 x i64> @test_insertq_call_constexpr(<2 x i64> %x) {
; CHECK-LABEL: @test_insertq_call_constexpr(
; CHECK-NEXT: [[TMP1:%.*]] = tail call <2 x i64> @llvm.x86.sse4a.insertq(<2 x i64> %x, <2 x i64> bitcast (<16 x i8> trunc (<16 x i16> bitcast (<4 x i64> <i64 0, i64 undef, i64 2, i64 undef> to <16 x i16>) to <16 x i8>) to <2 x i64>))
; CHECK-NEXT: [[TMP1:%.*]] = call <2 x i64> @llvm.x86.sse4a.insertqi(<2 x i64> %x, <2 x i64> <i64 0, i64 undef>, i8 2, i8 0)
; CHECK-NEXT: ret <2 x i64> [[TMP1]]
;
%1 = tail call <2 x i64> @llvm.x86.sse4a.insertq(<2 x i64> %x, <2 x i64> bitcast (<16 x i8> trunc (<16 x i16> bitcast (<4 x i64> <i64 0, i64 undef, i64 2, i64 undef> to <16 x i16>) to <16 x i8>) to <2 x i64>))
@ -224,7 +223,7 @@ define <2 x i64> @test_insertqi_constant(<2 x i64> %v, <2 x i64> %i) {
define <2 x i64> @test_insertqi_call_constexpr(<2 x i64> %x) {
; CHECK-LABEL: @test_insertqi_call_constexpr(
; CHECK-NEXT: [[TMP1:%.*]] = tail call <2 x i64> @llvm.x86.sse4a.insertqi(<2 x i64> %x, <2 x i64> bitcast (<16 x i8> trunc (<16 x i16> bitcast (<4 x i64> <i64 0, i64 undef, i64 2, i64 undef> to <16 x i16>) to <16 x i8>) to <2 x i64>), i8 48, i8 3)
; CHECK-NEXT: [[TMP1:%.*]] = tail call <2 x i64> @llvm.x86.sse4a.insertqi(<2 x i64> %x, <2 x i64> <i64 0, i64 undef>, i8 48, i8 3)
; CHECK-NEXT: ret <2 x i64> [[TMP1]]
;
%1 = tail call <2 x i64> @llvm.x86.sse4a.insertqi(<2 x i64> %x, <2 x i64> bitcast (<16 x i8> trunc (<16 x i16> bitcast (<4 x i64> <i64 0, i64 undef, i64 2, i64 undef> to <16 x i16>) to <16 x i8>) to <2 x i64>), i8 48, i8 3)

36
llvm/test/Transforms/InstSimplify/bitcast-vector-fold.ll
View File

@ -126,7 +126,7 @@ define <2 x double> @foo6() {
define <4 x i32> @bitcast_constexpr_4i32_2i64_u2() {
; CHECK-LABEL: @bitcast_constexpr_4i32_2i64_u2(
; CHECK-NEXT: ret <4 x i32> bitcast (<2 x i64> <i64 undef, i64 2> to <4 x i32>)
; CHECK-NEXT: ret <4 x i32> <i32 undef, i32 undef, i32 2, i32 0>
;
%cast = bitcast <2 x i64><i64 undef, i64 2> to <4 x i32>
ret <4 x i32> %cast
@ -134,7 +134,7 @@ define <4 x i32> @bitcast_constexpr_4i32_2i64_u2() {
define <4 x i32> @bitcast_constexpr_4i32_2i64_1u() {
; CHECK-LABEL: @bitcast_constexpr_4i32_2i64_1u(
; CHECK-NEXT: ret <4 x i32> bitcast (<2 x i64> <i64 1, i64 undef> to <4 x i32>)
; CHECK-NEXT: ret <4 x i32> <i32 1, i32 0, i32 undef, i32 undef>
;
%cast = bitcast <2 x i64><i64 1, i64 undef> to <4 x i32>
ret <4 x i32> %cast
@ -142,7 +142,7 @@ define <4 x i32> @bitcast_constexpr_4i32_2i64_1u() {
define <4 x i32> @bitcast_constexpr_4i32_2i64() {
; CHECK-LABEL: @bitcast_constexpr_4i32_2i64(
; CHECK-NEXT: ret <4 x i32> bitcast (<2 x i64> <i64 undef, i64 2> to <4 x i32>)
; CHECK-NEXT: ret <4 x i32> <i32 undef, i32 undef, i32 2, i32 0>
;
%cast = bitcast <2 x i64><i64 undef, i64 2> to <4 x i32>
ret <4 x i32> %cast
@ -150,7 +150,7 @@ define <4 x i32> @bitcast_constexpr_4i32_2i64() {
define <8 x i16> @bitcast_constexpr_8i16_2i64_u2() {
; CHECK-LABEL: @bitcast_constexpr_8i16_2i64_u2(
; CHECK-NEXT: ret <8 x i16> bitcast (<2 x i64> <i64 undef, i64 2> to <8 x i16>)
; CHECK-NEXT: ret <8 x i16> <i16 undef, i16 undef, i16 undef, i16 undef, i16 2, i16 0, i16 0, i16 0>
;
%cast = bitcast <2 x i64><i64 undef, i64 2> to <8 x i16>
ret <8 x i16> %cast
@ -158,7 +158,7 @@ define <8 x i16> @bitcast_constexpr_8i16_2i64_u2() {
define <8 x i16> @bitcast_constexpr_8i16_2i64_1u() {
; CHECK-LABEL: @bitcast_constexpr_8i16_2i64_1u(
; CHECK-NEXT: ret <8 x i16> bitcast (<2 x i64> <i64 1, i64 undef> to <8 x i16>)
; CHECK-NEXT: ret <8 x i16> <i16 1, i16 0, i16 0, i16 0, i16 undef, i16 undef, i16 undef, i16 undef>
;
%cast = bitcast <2 x i64><i64 1, i64 undef> to <8 x i16>
ret <8 x i16> %cast
@ -166,7 +166,7 @@ define <8 x i16> @bitcast_constexpr_8i16_2i64_1u() {
define <8 x i16> @bitcast_constexpr_8i16_2i64_u65536() {
; CHECK-LABEL: @bitcast_constexpr_8i16_2i64_u65536(
; CHECK-NEXT: ret <8 x i16> bitcast (<2 x i64> <i64 undef, i64 65536> to <8 x i16>)
; CHECK-NEXT: ret <8 x i16> <i16 undef, i16 undef, i16 undef, i16 undef, i16 0, i16 1, i16 0, i16 0>
;
%cast = bitcast <2 x i64><i64 undef, i64 65536> to <8 x i16>
ret <8 x i16> %cast
@ -174,7 +174,7 @@ define <8 x i16> @bitcast_constexpr_8i16_2i64_u65536() {
define <16 x i8> @bitcast_constexpr_16i8_2i64_u2() {
; CHECK-LABEL: @bitcast_constexpr_16i8_2i64_u2(
; CHECK-NEXT: ret <16 x i8> bitcast (<2 x i64> <i64 undef, i64 2> to <16 x i8>)
; CHECK-NEXT: ret <16 x i8> <i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 2, i8 0, i8 0, i8 0, i8 0, i8 0, i8 0, i8 0>
;
%cast = bitcast <2 x i64><i64 undef, i64 2> to <16 x i8>
ret <16 x i8> %cast
@ -182,7 +182,7 @@ define <16 x i8> @bitcast_constexpr_16i8_2i64_u2() {
define <16 x i8> @bitcast_constexpr_16i8_2i64_256u() {
; CHECK-LABEL: @bitcast_constexpr_16i8_2i64_256u(
; CHECK-NEXT: ret <16 x i8> bitcast (<2 x i64> <i64 256, i64 undef> to <16 x i8>)
; CHECK-NEXT: ret <16 x i8> <i8 0, i8 1, i8 0, i8 0, i8 0, i8 0, i8 0, i8 0, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef>
;
%cast = bitcast <2 x i64><i64 256, i64 undef> to <16 x i8>
ret <16 x i8> %cast
@ -190,7 +190,7 @@ define <16 x i8> @bitcast_constexpr_16i8_2i64_256u() {
define <16 x i8> @bitcast_constexpr_16i8_2i64_u256() {
; CHECK-LABEL: @bitcast_constexpr_16i8_2i64_u256(
; CHECK-NEXT: ret <16 x i8> bitcast (<2 x i64> <i64 undef, i64 256> to <16 x i8>)
; CHECK-NEXT: ret <16 x i8> <i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 0, i8 1, i8 0, i8 0, i8 0, i8 0, i8 0, i8 0>
;
%cast = bitcast <2 x i64><i64 undef, i64 256> to <16 x i8>
ret <16 x i8> %cast
@ -198,7 +198,7 @@ define <16 x i8> @bitcast_constexpr_16i8_2i64_u256() {
define <8 x i16> @bitcast_constexpr_8i16_4i32_uu22() {
; CHECK-LABEL: @bitcast_constexpr_8i16_4i32_uu22(
; CHECK-NEXT: ret <8 x i16> bitcast (<4 x i32> <i32 undef, i32 undef, i32 2, i32 2> to <8 x i16>)
; CHECK-NEXT: ret <8 x i16> <i16 undef, i16 undef, i16 undef, i16 undef, i16 2, i16 0, i16 2, i16 0>
;
%cast = bitcast <4 x i32><i32 undef, i32 undef, i32 2, i32 2> to <8 x i16>
ret <8 x i16> %cast
@ -206,7 +206,7 @@ define <8 x i16> @bitcast_constexpr_8i16_4i32_uu22() {
define <8 x i16> @bitcast_constexpr_8i16_4i32_10uu() {
; CHECK-LABEL: @bitcast_constexpr_8i16_4i32_10uu(
; CHECK-NEXT: ret <8 x i16> bitcast (<4 x i32> <i32 1, i32 0, i32 undef, i32 undef> to <8 x i16>)
; CHECK-NEXT: ret <8 x i16> <i16 1, i16 0, i16 0, i16 0, i16 undef, i16 undef, i16 undef, i16 undef>
;
%cast = bitcast <4 x i32><i32 1, i32 0, i32 undef, i32 undef> to <8 x i16>
ret <8 x i16> %cast
@ -214,7 +214,7 @@ define <8 x i16> @bitcast_constexpr_8i16_4i32_10uu() {
define <8 x i16> @bitcast_constexpr_8i16_4i32_u257u256() {
; CHECK-LABEL: @bitcast_constexpr_8i16_4i32_u257u256(
; CHECK-NEXT: ret <8 x i16> bitcast (<4 x i32> <i32 undef, i32 65536, i32 undef, i32 65536> to <8 x i16>)
; CHECK-NEXT: ret <8 x i16> <i16 undef, i16 undef, i16 0, i16 1, i16 undef, i16 undef, i16 0, i16 1>
;
%cast = bitcast <4 x i32><i32 undef, i32 65536, i32 undef, i32 65536> to <8 x i16>
ret <8 x i16> %cast
@ -222,7 +222,7 @@ define <8 x i16> @bitcast_constexpr_8i16_4i32_u257u256() {
define <16 x i8> @bitcast_constexpr_16i8_4i32_u2u2() {
; CHECK-LABEL: @bitcast_constexpr_16i8_4i32_u2u2(
; CHECK-NEXT: ret <16 x i8> bitcast (<4 x i32> <i32 undef, i32 2, i32 undef, i32 2> to <16 x i8>)
; CHECK-NEXT: ret <16 x i8> <i8 undef, i8 undef, i8 undef, i8 undef, i8 2, i8 0, i8 0, i8 0, i8 undef, i8 undef, i8 undef, i8 undef, i8 2, i8 0, i8 0, i8 0>
;
%cast = bitcast <4 x i32><i32 undef, i32 2, i32 undef, i32 2> to <16 x i8>
ret <16 x i8> %cast
@ -230,7 +230,7 @@ define <16 x i8> @bitcast_constexpr_16i8_4i32_u2u2() {
define <16 x i8> @bitcast_constexpr_16i8_4i32_1u1u() {
; CHECK-LABEL: @bitcast_constexpr_16i8_4i32_1u1u(
; CHECK-NEXT: ret <16 x i8> bitcast (<4 x i32> <i32 1, i32 undef, i32 1, i32 undef> to <16 x i8>)
; CHECK-NEXT: ret <16 x i8> <i8 1, i8 0, i8 0, i8 0, i8 undef, i8 undef, i8 undef, i8 undef, i8 1, i8 0, i8 0, i8 0, i8 undef, i8 undef, i8 undef, i8 undef>
;
%cast = bitcast <4 x i32><i32 1, i32 undef, i32 1, i32 undef> to <16 x i8>
ret <16 x i8> %cast
@ -238,7 +238,7 @@ define <16 x i8> @bitcast_constexpr_16i8_4i32_1u1u() {
define <16 x i8> @bitcast_constexpr_16i8_4i32_u256uu() {
; CHECK-LABEL: @bitcast_constexpr_16i8_4i32_u256uu(
; CHECK-NEXT: ret <16 x i8> bitcast (<4 x i32> <i32 undef, i32 256, i32 undef, i32 undef> to <16 x i8>)
; CHECK-NEXT: ret <16 x i8> <i8 undef, i8 undef, i8 undef, i8 undef, i8 0, i8 1, i8 0, i8 0, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef>
;
%cast = bitcast <4 x i32><i32 undef, i32 256, i32 undef, i32 undef> to <16 x i8>
ret <16 x i8> %cast
@ -246,7 +246,7 @@ define <16 x i8> @bitcast_constexpr_16i8_4i32_u256uu() {
define <16 x i8> @bitcast_constexpr_16i8_8i16_u2u2u2u2() {
; CHECK-LABEL: @bitcast_constexpr_16i8_8i16_u2u2u2u2(
; CHECK-NEXT: ret <16 x i8> bitcast (<8 x i16> <i16 undef, i16 2, i16 undef, i16 2, i16 undef, i16 2, i16 undef, i16 2> to <16 x i8>)
; CHECK-NEXT: ret <16 x i8> <i8 undef, i8 undef, i8 2, i8 0, i8 undef, i8 undef, i8 2, i8 0, i8 undef, i8 undef, i8 2, i8 0, i8 undef, i8 undef, i8 2, i8 0>
;
%cast = bitcast <8 x i16><i16 undef, i16 2, i16 undef, i16 2, i16 undef, i16 2, i16 undef, i16 2> to <16 x i8>
ret <16 x i8> %cast
@ -254,7 +254,7 @@ define <16 x i8> @bitcast_constexpr_16i8_8i16_u2u2u2u2() {
define <16 x i8> @bitcast_constexpr_16i8_8i16_1u1u1u1u() {
; CHECK-LABEL: @bitcast_constexpr_16i8_8i16_1u1u1u1u(
; CHECK-NEXT: ret <16 x i8> bitcast (<8 x i16> <i16 1, i16 undef, i16 1, i16 undef, i16 1, i16 undef, i16 1, i16 undef> to <16 x i8>)
; CHECK-NEXT: ret <16 x i8> <i8 1, i8 0, i8 undef, i8 undef, i8 1, i8 0, i8 undef, i8 undef, i8 1, i8 0, i8 undef, i8 undef, i8 1, i8 0, i8 undef, i8 undef>
;
%cast = bitcast <8 x i16><i16 1, i16 undef, i16 1, i16 undef, i16 1, i16 undef, i16 1, i16 undef> to <16 x i8>
ret <16 x i8> %cast
@ -262,7 +262,7 @@ define <16 x i8> @bitcast_constexpr_16i8_8i16_1u1u1u1u() {
define <16 x i8> @bitcast_constexpr_16i8_8i16_u256uuu256uu() {
; CHECK-LABEL: @bitcast_constexpr_16i8_8i16_u256uuu256uu(
; CHECK-NEXT: ret <16 x i8> bitcast (<8 x i16> <i16 undef, i16 256, i16 undef, i16 undef, i16 undef, i16 256, i16 undef, i16 undef> to <16 x i8>)
; CHECK-NEXT: ret <16 x i8> <i8 undef, i8 undef, i8 0, i8 1, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 undef, i8 0, i8 1, i8 undef, i8 undef, i8 undef, i8 undef>
;
%cast = bitcast <8 x i16><i16 undef, i16 256, i16 undef, i16 undef, i16 undef, i16 256, i16 undef, i16 undef> to <16 x i8>
ret <16 x i8> %cast