From b51a68681a005a0f209094438d08d92affda6679 Mon Sep 17 00:00:00 2001 From: Quentin Colombet Date: Tue, 18 Jun 2013 20:14:39 +0000 Subject: [PATCH] During SelectionDAG building explicitly set a node to constant zero when the value is zero. This allows optmizations to kick in more easily. Fix some test cases so that they remain meaningful (i.e., not completely dead coded) when optimizations apply. superfluous multiply by high part of zero-extended value. llvm-svn: 184222 --- .../SelectionDAG/SelectionDAGBuilder.cpp | 8 +++++ llvm/test/CodeGen/ARM/mvn.ll | 2 +- .../X86/2007-10-12-CoalesceExtSubReg.ll | 6 ++-- .../CodeGen/X86/2008-01-08-SchedulerCrash.ll | 2 +- llvm/test/CodeGen/X86/i128-mul.ll | 36 ++++++++++++++++++- 5 files changed, 49 insertions(+), 5 deletions(-) diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp index 608fc275b5a9..a45485382ade 100644 --- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp @@ -718,6 +718,14 @@ SDValue RegsForValue::getCopyFromRegs(SelectionDAG &DAG, unsigned NumSignBits = LOI->NumSignBits; unsigned NumZeroBits = LOI->KnownZero.countLeadingOnes(); + if (NumZeroBits == RegSize) { + // The current value is a zero. + // Explicitly express that as it would be easier for + // optimizations to kick in. + Parts[i] = DAG.getConstant(0, RegisterVT); + continue; + } + // FIXME: We capture more information than the dag can represent. For // now, just use the tightest assertzext/assertsext possible. bool isSExt = true; diff --git a/llvm/test/CodeGen/ARM/mvn.ll b/llvm/test/CodeGen/ARM/mvn.ll index 571c21a833ec..2c5ccd7442e0 100644 --- a/llvm/test/CodeGen/ARM/mvn.ll +++ b/llvm/test/CodeGen/ARM/mvn.ll @@ -1,4 +1,4 @@ -; RUN: llc < %s -march=arm | grep mvn | count 8 +; RUN: llc < %s -march=arm | grep mvn | count 9 define i32 @f1() { entry: diff --git a/llvm/test/CodeGen/X86/2007-10-12-CoalesceExtSubReg.ll b/llvm/test/CodeGen/X86/2007-10-12-CoalesceExtSubReg.ll index 8091bd1bc1ca..d3a47aefb7d0 100644 --- a/llvm/test/CodeGen/X86/2007-10-12-CoalesceExtSubReg.ll +++ b/llvm/test/CodeGen/X86/2007-10-12-CoalesceExtSubReg.ll @@ -7,8 +7,10 @@ entry: cond_next127: ; preds = %cond_next391, %entry %v.1 = phi i32 [ undef, %entry ], [ %tmp411, %cond_next391 ] ; [#uses=1] %tmp149 = mul i32 0, %v.1 ; [#uses=0] - %tmp254 = and i32 0, 15 ; [#uses=1] - %tmp256 = and i32 0, 15 ; [#uses=2] + %tmpss = load i32* %ss, align 4 ; [#uses=1] + %tmpbp = load i32* %bp, align 4 ; [#uses=2] + %tmp254 = and i32 %tmpss, 15 ; [#uses=1] + %tmp256 = and i32 %tmpbp, 15 ; [#uses=2] br label %cond_next391 cond_next391: ; preds = %cond_next127 diff --git a/llvm/test/CodeGen/X86/2008-01-08-SchedulerCrash.ll b/llvm/test/CodeGen/X86/2008-01-08-SchedulerCrash.ll index 39af9319c8d1..9b9b781cfa2e 100644 --- a/llvm/test/CodeGen/X86/2008-01-08-SchedulerCrash.ll +++ b/llvm/test/CodeGen/X86/2008-01-08-SchedulerCrash.ll @@ -19,7 +19,7 @@ bb917: ; preds = %entry ret i32 0 bb951: ; preds = %bb986, %entry - %tmp955 = sdiv i32 0, 2 ; [#uses=3] + %tmp955 = sdiv i32 %offset, 2 ; [#uses=3] %tmp961 = getelementptr %struct.indexentry* null, i32 %tmp955, i32 0 ; [#uses=1] br i1 %cond, label %bb986, label %bb967 diff --git a/llvm/test/CodeGen/X86/i128-mul.ll b/llvm/test/CodeGen/X86/i128-mul.ll index e9d30d67019e..c0b85dfd211b 100644 --- a/llvm/test/CodeGen/X86/i128-mul.ll +++ b/llvm/test/CodeGen/X86/i128-mul.ll @@ -1,4 +1,4 @@ -; RUN: llc < %s -march=x86-64 +; RUN: llc < %s -march=x86-64 | FileCheck %s ; PR1198 define i64 @foo(i64 %x, i64 %y) { @@ -10,3 +10,37 @@ define i64 @foo(i64 %x, i64 %y) { %tmp4 = trunc i128 %tmp3 to i64 ret i64 %tmp4 } + +; superfluous multiply by high part of +; zero-extended value. +; CHECK: @mul1 +; CHECK-NOT: imulq +; CHECK: mulq +; CHECK-NOT: imulq +define i64 @mul1(i64 %n, i64* nocapture %z, i64* nocapture %x, i64 %y) { +entry: + %conv = zext i64 %y to i128 + %cmp11 = icmp eq i64 %n, 0 + br i1 %cmp11, label %for.end, label %for.body + +for.body: ; preds = %entry, %for.body + %carry.013 = phi i64 [ %conv6, %for.body ], [ 0, %entry ] + %i.012 = phi i64 [ %inc, %for.body ], [ 0, %entry ] + %arrayidx = getelementptr inbounds i64* %x, i64 %i.012 + %0 = load i64* %arrayidx, align 8 + %conv2 = zext i64 %0 to i128 + %mul = mul i128 %conv2, %conv + %conv3 = zext i64 %carry.013 to i128 + %add = add i128 %mul, %conv3 + %conv4 = trunc i128 %add to i64 + %arrayidx5 = getelementptr inbounds i64* %z, i64 %i.012 + store i64 %conv4, i64* %arrayidx5, align 8 + %shr = lshr i128 %add, 64 + %conv6 = trunc i128 %shr to i64 + %inc = add i64 %i.012, 1 + %exitcond = icmp eq i64 %inc, %n + br i1 %exitcond, label %for.end, label %for.body + +for.end: ; preds = %for.body, %entry + ret i64 0 +}