[llvm-commits] [llvm] r147036 - in /llvm/trunk: lib/Analysis/ValueTracking.cpp lib/Transforms/Utils/SimplifyCFG.cpp test/Transforms/SimplifyCFG/SpeculativeExec.ll
Nick Lewycky
nicholas at mxc.ca
Tue Dec 20 21:52:02 PST 2011
Author: nicholas
Date: Tue Dec 20 23:52:02 2011
New Revision: 147036
URL: http://llvm.org/viewvc/llvm-project?rev=147036&view=rev
Log:
Make some intrinsics safe to speculatively execute.
Modified:
llvm/trunk/lib/Analysis/ValueTracking.cpp
llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/trunk/test/Transforms/SimplifyCFG/SpeculativeExec.ll
Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=147036&r1=147035&r2=147036&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp Tue Dec 20 23:52:02 2011
@@ -1912,11 +1912,31 @@
return false;
return LI->getPointerOperand()->isDereferenceablePointer();
}
- case Instruction::Call:
+ case Instruction::Call: {
+ if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
+ switch (II->getIntrinsicID()) {
+ case Intrinsic::bswap:
+ case Intrinsic::ctlz:
+ case Intrinsic::ctpop:
+ case Intrinsic::cttz:
+ case Intrinsic::objectsize:
+ case Intrinsic::sadd_with_overflow:
+ case Intrinsic::smul_with_overflow:
+ case Intrinsic::ssub_with_overflow:
+ case Intrinsic::uadd_with_overflow:
+ case Intrinsic::umul_with_overflow:
+ case Intrinsic::usub_with_overflow:
+ return true;
+ // TODO: some fp intrinsics are marked as having the same error handling
+ // as libm. They're safe to speculate when they won't error.
+ // TODO: are convert_{from,to}_fp16 safe?
+ // TODO: can we list target-specific intrinsics here?
+ default: break;
+ }
+ }
return false; // The called function could have undefined behavior or
- // side-effects.
- // FIXME: We should special-case some intrinsics (bswap,
- // overflow-checking arithmetic, etc.)
+ // side-effects, even if marked readnone nounwind.
+ }
case Instruction::VAArg:
case Instruction::Alloca:
case Instruction::Invoke:
Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=147036&r1=147035&r2=147036&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Tue Dec 20 23:52:02 2011
@@ -293,6 +293,7 @@
Cost = 1;
break; // These are all cheap and non-trapping instructions.
+ case Instruction::Call:
case Instruction::Select:
Cost = 2;
break;
Modified: llvm/trunk/test/Transforms/SimplifyCFG/SpeculativeExec.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/SpeculativeExec.ll?rev=147036&r1=147035&r2=147036&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/SpeculativeExec.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/SpeculativeExec.ll Tue Dec 20 23:52:02 2011
@@ -1,7 +1,10 @@
-; RUN: opt < %s -simplifycfg -S | grep select
-; RUN: opt < %s -simplifycfg -S | grep br | count 2
+; RUN: opt < %s -simplifycfg -phi-node-folding-threshold=2 -S | FileCheck %s
-define i32 @t2(i32 %a, i32 %b, i32 %c) nounwind {
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define i32 @test1(i32 %a, i32 %b, i32 %c) nounwind {
+; CHECK: @test1
entry:
%tmp1 = icmp eq i32 %b, 0
br i1 %tmp1, label %bb1, label %bb3
@@ -9,6 +12,11 @@
bb1: ; preds = %entry
%tmp2 = icmp sgt i32 %c, 1
br i1 %tmp2, label %bb2, label %bb3
+; CHECK: bb1:
+; CHECK-NEXT: add i32 %a, 1
+; CHECK-NEXT: icmp sgt i32 %c, 1
+; CHECK-NEXT: select i1 %tmp2, i32 %tmp3, i32 %a
+; CHECK-NEXT: br label %bb3
bb2: ; preds = bb1
%tmp3 = add i32 %a, 1
@@ -19,3 +27,20 @@
%tmp5 = sub i32 %tmp4, 1
ret i32 %tmp5
}
+
+declare i8 @llvm.cttz.i8(i8, i1)
+
+define i8 @test2(i8 %a) {
+; CHECK: @test2
+ br i1 undef, label %bb_true, label %bb_false
+bb_true:
+ %b = tail call i8 @llvm.cttz.i8(i8 %a, i1 false)
+ br label %join
+bb_false:
+ br label %join
+join:
+ %c = phi i8 [%b, %bb_true], [%a, %bb_false]
+; CHECK: select
+ ret i8 %c
+}
+
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