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[InstCombine] collectBitParts - add trunc support.

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This should allow us to remove the rather limited matchOrConcat fold and just use recognizeBSwapOrBitReverseIdiom.
This commit is contained in:
Simon Pilgrim 2020-10-26 16:22:46 +00:00
parent d3e8393700
commit 3e4f2ad439
2 changed files with 15 additions and 14 deletions
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15
lib/Transforms/Utils/Local.cpp
View File

@ -2928,7 +2928,7 @@ collectBitParts(Value *V, bool MatchBSwaps, bool MatchBitReversals,
return Result;
}
// If this is a zext instruction zero extend the result.
// If this is a zext instruction, zero extend the result.
if (match(V, m_ZExt(m_Value(X)))) {
const auto &Res =
collectBitParts(X, MatchBSwaps, MatchBitReversals, BPS, Depth + 1);
@ -2944,6 +2944,19 @@ collectBitParts(Value *V, bool MatchBSwaps, bool MatchBitReversals,
return Result;
}
// If this is a trunc instruction, take the lower bits.
if (match(V, m_Trunc(m_Value(X)))) {
const auto &Res =
collectBitParts(X, MatchBSwaps, MatchBitReversals, BPS, Depth + 1);
if (!Res)
return Result;
Result = BitPart(Res->Provider, BitWidth);
for (unsigned BitIdx = 0; BitIdx < BitWidth; ++BitIdx)
Result->Provenance[BitIdx] = Res->Provenance[BitIdx];
return Result;
}
// BITREVERSE - most likely due to us previous matching a partial
// bitreverse.
if (match(V, m_BitReverse(m_Value(X)))) {

14
test/Transforms/InstCombine/bswap.ll
View File

@ -596,19 +596,7 @@ define i64 @bswap_and_mask_2(i64 %0) {
define i64 @bswap_trunc(i64 %x01234567) {
; CHECK-LABEL: @bswap_trunc(
; CHECK-NEXT: [[X7ZZZZZZZ:%.*]] = shl i64 [[X01234567:%.*]], 56
; CHECK-NEXT: [[XZ0123456:%.*]] = lshr i64 [[X01234567]], 8
; CHECK-NEXT: [[XZZZZZ012:%.*]] = lshr i64 [[X01234567]], 40
; CHECK-NEXT: [[X3456:%.*]] = trunc i64 [[XZ0123456]] to i32
; CHECK-NEXT: [[XZ012:%.*]] = trunc i64 [[XZZZZZ012]] to i32
; CHECK-NEXT: [[X6543:%.*]] = call i32 @llvm.bswap.i32(i32 [[X3456]])
; CHECK-NEXT: [[X210Z:%.*]] = call i32 @llvm.bswap.i32(i32 [[XZ012]])
; CHECK-NEXT: [[XZ210:%.*]] = lshr exact i32 [[X210Z]], 8
; CHECK-NEXT: [[XZZZZ6543:%.*]] = zext i32 [[X6543]] to i64
; CHECK-NEXT: [[XZZZZZ210:%.*]] = zext i32 [[XZ210]] to i64
; CHECK-NEXT: [[XZ6543ZZZ:%.*]] = shl nuw nsw i64 [[XZZZZ6543]], 24
; CHECK-NEXT: [[XZ6543210:%.*]] = or i64 [[XZ6543ZZZ]], [[XZZZZZ210]]
; CHECK-NEXT: [[X76543210:%.*]] = or i64 [[XZ6543210]], [[X7ZZZZZZZ]]
; CHECK-NEXT: [[X76543210:%.*]] = call i64 @llvm.bswap.i64(i64 [[X01234567:%.*]])
; CHECK-NEXT: ret i64 [[X76543210]]
;
%x7zzzzzzz = shl i64 %x01234567, 56