[llvm-commits] [llvm] r146822 - in /llvm/trunk: lib/Transforms/Utils/SimplifyCFG.cpp test/Transforms/SimplifyCFG/PredictNestedBranch.ll
Peter Cooper
peter_cooper at apple.com
Sat Dec 17 09:50:43 PST 2011
Hi
I'm not at my computer but this commit broke clang self hosting. Can someone with commit access please revert it and i'll try fix it on Monday.
Thanks
Pete
Sent from my iPhone
On Dec 16, 2011, at 10:32 PM, Pete Cooper <peter_cooper at apple.com> wrote:
> Author: pete
> Date: Sat Dec 17 00:32:38 2011
> New Revision: 146822
>
> URL: http://llvm.org/viewvc/llvm-project?rev=146822&view=rev
> Log:
> SimplifyCFG now predicts some conditional branches to true or false depending on previous branch on same comparison operands.
>
> For example,
>
> if (a == b) {
> if (a > b) // this is false
>
> Fixes some of the issues on <rdar://problem/10554090>
>
> Added:
> llvm/trunk/test/Transforms/SimplifyCFG/PredictNestedBranch.ll
> Modified:
> llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
>
> Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=146822&r1=146821&r2=146822&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
> +++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Sat Dec 17 00:32:38 2011
> @@ -12,6 +12,7 @@
> //===----------------------------------------------------------------------===//
>
> #define DEBUG_TYPE "simplifycfg"
> +#include "llvm/Transforms/Utils/CmpInstAnalysis.h"
> #include "llvm/Transforms/Utils/Local.h"
> #include "llvm/Constants.h"
> #include "llvm/Instructions.h"
> @@ -1702,6 +1703,47 @@
> }
> }
>
> + // Treat "if (cond1) { if (cond2) {} }" as "cond1 & cond2" and fold.
> + // This gives us the value of what cond2 is given cond1 is already known to
> + // be true.
> + if (ICmpInst *LHS = dyn_cast<ICmpInst>(PBI->getCondition())) {
> + if (ICmpInst *RHS = dyn_cast<ICmpInst>(BI->getCondition())) {
> + ICmpInst::Predicate LHSCC = LHS->getPredicate(),
> + RHSCC = RHS->getPredicate();
> + if (PredicatesFoldable(LHSCC, RHSCC)) {
> + if (LHS->getOperand(0) == RHS->getOperand(1) &&
> + LHS->getOperand(1) == RHS->getOperand(0))
> + LHS->swapOperands();
> + if (LHS->getOperand(0) == RHS->getOperand(0) &&
> + LHS->getOperand(1) == RHS->getOperand(1) &&
> + BB->getSinglePredecessor()) {
> + Value *Op0 = LHS->getOperand(0), *Op1 = LHS->getOperand(1);
> + bool CondIsTrue = PBI->getSuccessor(0) == BB;
> + unsigned LHSCode = getICmpCode(LHS, !CondIsTrue);
> + unsigned RHSCode = getICmpCode(RHS);
> + unsigned Code = LHSCode & RHSCode;
> +
> + Value *ConstantCondition = NULL;
> + // If the resultant code is the same as the LHS code then as that
> + // code is known to be true we can make RHS now be true.
> + if (Code == LHSCode)
> + ConstantCondition = ConstantInt::get(
> + CmpInst::makeCmpResultType(LHS->getType()), 1);
> + else {
> + bool isSigned = LHS->isSigned() || RHS->isSigned();
> + CmpInst::Predicate IgnoredNewPred;
> + ConstantCondition = getICmpValue(isSigned, Code, Op0, Op1,
> + IgnoredNewPred);
> + }
> + if (ConstantCondition) {
> + RHS->replaceAllUsesWith(ConstantCondition);
> + return true;
> + }
> + }
> + }
> + }
> + }
> +
> // If this is a conditional branch in an empty block, and if any
> // predecessors is a conditional branch to one of our destinations,
> // fold the conditions into logical ops and one cond br.
>
> Added: llvm/trunk/test/Transforms/SimplifyCFG/PredictNestedBranch.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/PredictNestedBranch.ll?rev=146822&view=auto
> ==============================================================================
> --- llvm/trunk/test/Transforms/SimplifyCFG/PredictNestedBranch.ll (added)
> +++ llvm/trunk/test/Transforms/SimplifyCFG/PredictNestedBranch.ll Sat Dec 17 00:32:38 2011
> @@ -0,0 +1,152 @@
> +
> +; RUN: opt < %s -simplifycfg -dce -S | FileCheck %s
> +
> +; Test that when == is true, all 6 comparisons evaluate to true or false
> +; ie, a == b implies a > b is false, but a >= b is true, and so on
> +define void @testEqTrue(i32 %a, i32 %b) {
> +; CHECK: @testEqTrue
> +; CHECK: icmp eq i32 %a, %b
> +; CHECK: call void @_Z1gi(i32 0)
> +; a == b implies a == b
> +; CHECK-NEXT: call void @_Z1gi(i32 1)
> +; a == b implies a >= b
> +; CHECK-NEXT: call void @_Z1gi(i32 3)
> +; a == b implies a <= b
> +; CHECK-NEXT: call void @_Z1gi(i32 4)
> +; CHECK: ret void
> +entry:
> + %cmp = icmp eq i32 %a, %b
> + br i1 %cmp, label %if.then, label %if.end18
> +
> +if.then: ; preds = %entry
> + call void @_Z1gi(i32 0)
> + %cmp1 = icmp eq i32 %a, %b
> + br i1 %cmp1, label %if.then2, label %if.end
> +
> +if.then2: ; preds = %if.then
> + call void @_Z1gi(i32 1)
> + br label %if.end
> +
> +if.end: ; preds = %if.then2, %if.then
> + %cmp3 = icmp ne i32 %a, %b
> + br i1 %cmp3, label %if.then4, label %if.end5
> +
> +if.then4: ; preds = %if.end
> + call void @_Z1gi(i32 2)
> + br label %if.end5
> +
> +if.end5: ; preds = %if.then4, %if.end
> + %cmp6 = icmp sge i32 %a, %b
> + br i1 %cmp6, label %if.then7, label %if.end8
> +
> +if.then7: ; preds = %if.end5
> + call void @_Z1gi(i32 3)
> + br label %if.end8
> +
> +if.end8: ; preds = %if.then7, %if.end5
> + %cmp9 = icmp sle i32 %a, %b
> + br i1 %cmp9, label %if.then10, label %if.end11
> +
> +if.then10: ; preds = %if.end8
> + call void @_Z1gi(i32 4)
> + br label %if.end11
> +
> +if.end11: ; preds = %if.then10, %if.end8
> + %cmp12 = icmp sgt i32 %a, %b
> + br i1 %cmp12, label %if.then13, label %if.end14
> +
> +if.then13: ; preds = %if.end11
> + call void @_Z1gi(i32 5)
> + br label %if.end14
> +
> +if.end14: ; preds = %if.then13, %if.end11
> + %cmp15 = icmp slt i32 %a, %b
> + br i1 %cmp15, label %if.then16, label %if.end18
> +
> +if.then16: ; preds = %if.end14
> + call void @_Z1gi(i32 6)
> + br label %if.end18
> +
> +if.end18: ; preds = %if.end14, %if.then16, %entry
> + ret void
> +}
> +
> +; Test that when == is false, all 6 comparisons evaluate to true or false
> +; ie, a == b implies a > b is false, but a >= b is true, and so on
> +define void @testEqFalse(i32 %a, i32 %b) {
> +; CHECK: @testEqFalse
> +; CHECK: icmp eq i32 %a, %b
> +; CHECK: call void @_Z1gi(i32 0)
> +; CHECK-NOT: call void @_Z1gi(i32 1)
> +; CHECK-NOT: icmp ne
> +; CHECK: call void @_Z1gi(i32 2)
> +; CHECK: icmp sge
> +; CHECK: call void @_Z1gi(i32 3)
> +; CHECK: icmp sle
> +; CHECK: call void @_Z1gi(i32 4)
> +; CHECK: icmp sgt
> +; CHECK: call void @_Z1gi(i32 5)
> +; CHECK: icmp slt
> +; CHECK: call void @_Z1gi(i32 6)
> +; CHECK: ret void
> +entry:
> + %cmp = icmp eq i32 %a, %b
> + br i1 %cmp, label %if.then, label %if.else
> +
> +if.then: ; preds = %entry
> + call void @_Z1gi(i32 0)
> + br label %if.end18
> +
> +if.else:
> + %cmp1 = icmp eq i32 %a, %b
> + br i1 %cmp1, label %if.then2, label %if.end
> +
> +if.then2: ; preds = %if.then
> + call void @_Z1gi(i32 1)
> + br label %if.end
> +
> +if.end: ; preds = %if.then2, %if.then
> + %cmp3 = icmp ne i32 %a, %b
> + br i1 %cmp3, label %if.then4, label %if.end5
> +
> +if.then4: ; preds = %if.end
> + call void @_Z1gi(i32 2)
> + br label %if.end5
> +
> +if.end5: ; preds = %if.then4, %if.end
> + %cmp6 = icmp sge i32 %a, %b
> + br i1 %cmp6, label %if.then7, label %if.end8
> +
> +if.then7: ; preds = %if.end5
> + call void @_Z1gi(i32 3)
> + br label %if.end8
> +
> +if.end8: ; preds = %if.then7, %if.end5
> + %cmp9 = icmp sle i32 %a, %b
> + br i1 %cmp9, label %if.then10, label %if.end11
> +
> +if.then10: ; preds = %if.end8
> + call void @_Z1gi(i32 4)
> + br label %if.end11
> +
> +if.end11: ; preds = %if.then10, %if.end8
> + %cmp12 = icmp sgt i32 %a, %b
> + br i1 %cmp12, label %if.then13, label %if.end14
> +
> +if.then13: ; preds = %if.end11
> + call void @_Z1gi(i32 5)
> + br label %if.end14
> +
> +if.end14: ; preds = %if.then13, %if.end11
> + %cmp15 = icmp slt i32 %a, %b
> + br i1 %cmp15, label %if.then16, label %if.end18
> +
> +if.then16: ; preds = %if.end14
> + call void @_Z1gi(i32 6)
> + br label %if.end18
> +
> +if.end18: ; preds = %if.end14, %if.then16, %entry
> + ret void
> +}
> +
> +declare void @_Z1gi(i32)
>
>
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