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[CVP} Replace SExt with ZExt if the input is known-non-negative
Summary: zero-extension is far more friendly for further analysis. While this doesn't directly help with the shift-by-signext problem, this is not unrelated. This has the following effect on test-suite (numbers collected after the finish of middle-end module pass manager): | Statistic | old | new | delta | percent change | | correlated-value-propagation.NumSExt | 0 | 6026 | 6026 | +100.00% | | instcount.NumAddInst | 272860 | 271283 | -1577 | -0.58% | | instcount.NumAllocaInst | 27227 | 27226 | -1 | 0.00% | | instcount.NumAndInst | 63502 | 63320 | -182 | -0.29% | | instcount.NumAShrInst | 13498 | 13407 | -91 | -0.67% | | instcount.NumAtomicCmpXchgInst | 1159 | 1159 | 0 | 0.00% | | instcount.NumAtomicRMWInst | 5036 | 5036 | 0 | 0.00% | | instcount.NumBitCastInst | 672482 | 672353 | -129 | -0.02% | | instcount.NumBrInst | 702768 | 702195 | -573 | -0.08% | | instcount.NumCallInst | 518285 | 518205 | -80 | -0.02% | | instcount.NumExtractElementInst | 18481 | 18482 | 1 | 0.01% | | instcount.NumExtractValueInst | 18290 | 18288 | -2 | -0.01% | | instcount.NumFAddInst | 139035 | 138963 | -72 | -0.05% | | instcount.NumFCmpInst | 10358 | 10348 | -10 | -0.10% | | instcount.NumFDivInst | 30310 | 30302 | -8 | -0.03% | | instcount.NumFenceInst | 387 | 387 | 0 | 0.00% | | instcount.NumFMulInst | 93873 | 93806 | -67 | -0.07% | | instcount.NumFPExtInst | 7148 | 7144 | -4 | -0.06% | | instcount.NumFPToSIInst | 2823 | 2838 | 15 | 0.53% | | instcount.NumFPToUIInst | 1251 | 1251 | 0 | 0.00% | | instcount.NumFPTruncInst | 2195 | 2191 | -4 | -0.18% | | instcount.NumFSubInst | 92109 | 92103 | -6 | -0.01% | | instcount.NumGetElementPtrInst | 1221423 | 1219157 | -2266 | -0.19% | | instcount.NumICmpInst | 479140 | 478929 | -211 | -0.04% | | instcount.NumIndirectBrInst | 2 | 2 | 0 | 0.00% | | instcount.NumInsertElementInst | 66089 | 66094 | 5 | 0.01% | | instcount.NumInsertValueInst | 2032 | 2030 | -2 | -0.10% | | instcount.NumIntToPtrInst | 19641 | 19641 | 0 | 0.00% | | instcount.NumInvokeInst | 21789 | 21788 | -1 | 0.00% | | instcount.NumLandingPadInst | 12051 | 12051 | 0 | 0.00% | | instcount.NumLoadInst | 880079 | 878673 | -1406 | -0.16% | | instcount.NumLShrInst | 25919 | 25921 | 2 | 0.01% | | instcount.NumMulInst | 42416 | 42417 | 1 | 0.00% | | instcount.NumOrInst | 100826 | 100576 | -250 | -0.25% | | instcount.NumPHIInst | 315118 | 314092 | -1026 | -0.33% | | instcount.NumPtrToIntInst | 15933 | 15939 | 6 | 0.04% | | instcount.NumResumeInst | 2156 | 2156 | 0 | 0.00% | | instcount.NumRetInst | 84485 | 84484 | -1 | 0.00% | | instcount.NumSDivInst | 8599 | 8597 | -2 | -0.02% | | instcount.NumSelectInst | 45577 | 45913 | 336 | 0.74% | | instcount.NumSExtInst | 84026 | 78278 | -5748 | -6.84% | | instcount.NumShlInst | 39796 | 39726 | -70 | -0.18% | | instcount.NumShuffleVectorInst | 100272 | 100292 | 20 | 0.02% | | instcount.NumSIToFPInst | 29131 | 29113 | -18 | -0.06% | | instcount.NumSRemInst | 1543 | 1543 | 0 | 0.00% | | instcount.NumStoreInst | 805394 | 804351 | -1043 | -0.13% | | instcount.NumSubInst | 61337 | 61414 | 77 | 0.13% | | instcount.NumSwitchInst | 8527 | 8524 | -3 | -0.04% | | instcount.NumTruncInst | 60523 | 60484 | -39 | -0.06% | | instcount.NumUDivInst | 2381 | 2381 | 0 | 0.00% | | instcount.NumUIToFPInst | 5549 | 5549 | 0 | 0.00% | | instcount.NumUnreachableInst | 9855 | 9855 | 0 | 0.00% | | instcount.NumURemInst | 1305 | 1305 | 0 | 0.00% | | instcount.NumXorInst | 10230 | 10081 | -149 | -1.46% | | instcount.NumZExtInst | 60353 | 66840 | 6487 | 10.75% | | instcount.TotalBlocks | 829582 | 829004 | -578 | -0.07% | | instcount.TotalFuncs | 83818 | 83817 | -1 | 0.00% | | instcount.TotalInsts | 7316574 | 7308483 | -8091 | -0.11% | TLDR: we produce -0.11% less instructions, -6.84% less `sext`, +10.75% more `zext`. To be noted, clearly, not all new `zext`'s are produced by this fold. (And now i guess it might have been interesting to measure this for D68103 :S) Reviewers: nikic, spatel, reames, dberlin Reviewed By: nikic Subscribers: hiraditya, jfb, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D68654 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@374112 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Roman Lebedev
parent
e2796a6d06
commit
43122072b2
@ -62,6 +62,7 @@ STATISTIC(NumSDivs, "Number of sdiv converted to udiv");
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STATISTIC(NumUDivs, "Number of udivs whose width was decreased");
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STATISTIC(NumAShrs, "Number of ashr converted to lshr");
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STATISTIC(NumSRems, "Number of srem converted to urem");
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STATISTIC(NumSExt, "Number of sext converted to zext");
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STATISTIC(NumOverflows, "Number of overflow checks removed");
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STATISTIC(NumSaturating,
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"Number of saturating arithmetics converted to normal arithmetics");
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@ -637,6 +638,27 @@ static bool processAShr(BinaryOperator *SDI, LazyValueInfo *LVI) {
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return true;
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}
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static bool processSExt(SExtInst *SDI, LazyValueInfo *LVI) {
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if (SDI->getType()->isVectorTy())
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return false;
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Value *Base = SDI->getOperand(0);
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Constant *Zero = ConstantInt::get(Base->getType(), 0);
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if (LVI->getPredicateAt(ICmpInst::ICMP_SGE, Base, Zero, SDI) !=
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LazyValueInfo::True)
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return false;
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++NumSExt;
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auto *ZExt =
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CastInst::CreateZExtOrBitCast(Base, SDI->getType(), SDI->getName(), SDI);
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ZExt->setDebugLoc(SDI->getDebugLoc());
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SDI->replaceAllUsesWith(ZExt);
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SDI->eraseFromParent();
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return true;
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}
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static bool processBinOp(BinaryOperator *BinOp, LazyValueInfo *LVI) {
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using OBO = OverflowingBinaryOperator;
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@ -745,6 +767,9 @@ static bool runImpl(Function &F, LazyValueInfo *LVI, DominatorTree *DT,
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case Instruction::AShr:
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BBChanged |= processAShr(cast<BinaryOperator>(II), LVI);
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break;
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case Instruction::SExt:
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BBChanged |= processSExt(cast<SExtInst>(II), LVI);
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break;
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case Instruction::Add:
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case Instruction::Sub:
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BBChanged |= processBinOp(cast<BinaryOperator>(II), LVI);
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@ -18,9 +18,9 @@ define void @test1(i32 %n) {
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; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i32 [[A]], -1
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; CHECK-NEXT: br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
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; CHECK: for.body:
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; CHECK-NEXT: [[EXT_WIDE:%.*]] = sext i32 [[A]] to i64
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; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE]])
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; CHECK-NEXT: [[EXT]] = trunc i64 [[EXT_WIDE]] to i32
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; CHECK-NEXT: [[EXT_WIDE1:%.*]] = zext i32 [[A]] to i64
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; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE1]])
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; CHECK-NEXT: [[EXT]] = trunc i64 [[EXT_WIDE1]] to i32
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; CHECK-NEXT: br label [[FOR_COND]]
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; CHECK: for.end:
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; CHECK-NEXT: ret void
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@ -85,9 +85,9 @@ define void @test3(i32 %n) {
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; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i32 [[N:%.*]], -1
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; CHECK-NEXT: br i1 [[CMP]], label [[BB:%.*]], label [[EXIT:%.*]]
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; CHECK: bb:
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; CHECK-NEXT: [[EXT_WIDE:%.*]] = sext i32 [[N]] to i64
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; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE]])
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; CHECK-NEXT: [[EXT:%.*]] = trunc i64 [[EXT_WIDE]] to i32
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; CHECK-NEXT: [[EXT_WIDE1:%.*]] = zext i32 [[N]] to i64
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; CHECK-NEXT: call void @use64(i64 [[EXT_WIDE1]])
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; CHECK-NEXT: [[EXT:%.*]] = trunc i64 [[EXT_WIDE1]] to i32
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; CHECK-NEXT: br label [[EXIT]]
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; CHECK: exit:
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; CHECK-NEXT: ret void
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