[llvm] r268120 - [EarlyCSE] Simplify guard intrinsics
Sanjoy Das via llvm-commits
llvm-commits at lists.llvm.org
Fri Apr 29 14:52:59 PDT 2016
Author: sanjoy
Date: Fri Apr 29 16:52:58 2016
New Revision: 268120
URL: http://llvm.org/viewvc/llvm-project?rev=268120&view=rev
Log:
[EarlyCSE] Simplify guard intrinsics
Summary:
This change teaches EarlyCSE some basic properties of guard intrinsics:
- Guard intrinsics read all memory, but don't write to any memory
- After a guard has executed, the condition it was guarding on can be
assumed to be true
- Guard intrinsics on a constant `true` are no-ops
Reviewers: reames, hfinkel
Subscribers: mcrosier, llvm-commits
Differential Revision: http://reviews.llvm.org/D19578
Added:
llvm/trunk/test/Transforms/EarlyCSE/guards.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/EarlyCSE.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/EarlyCSE.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/EarlyCSE.cpp?rev=268120&r1=268119&r2=268120&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/EarlyCSE.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/EarlyCSE.cpp Fri Apr 29 16:52:58 2016
@@ -554,6 +554,29 @@ bool EarlyCSE::processNode(DomTreeNode *
continue;
}
+ if (match(Inst, m_Intrinsic<Intrinsic::experimental_guard>())) {
+ Value *Cond = cast<CallInst>(Inst)->getArgOperand(0);
+
+ if (match(Cond, m_One())) {
+ // Elide guards on true, since operationally they're no-ops. In the
+ // future we can consider more sophisticated tradeoffs here with
+ // consideration to potential for check widening, but for now we keep
+ // things simple.
+ Inst->eraseFromParent();
+ } else if (auto *CondI = dyn_cast<Instruction>(Cond)) {
+ // The condition we're on guarding here is true for all dominated
+ // locations.
+ if (SimpleValue::canHandle(CondI))
+ AvailableValues.insert(CondI, ConstantInt::getTrue(BB->getContext()));
+ }
+
+ // Guard intrinsics read all memory, but don't write any memory.
+ // Accordingly, don't update the generation but consume the last store (to
+ // avoid an incorrect DSE).
+ LastStore = nullptr;
+ continue;
+ }
+
// If the instruction can be simplified (e.g. X+0 = X) then replace it with
// its simpler value.
if (Value *V = SimplifyInstruction(Inst, DL, &TLI, &DT, &AC)) {
Added: llvm/trunk/test/Transforms/EarlyCSE/guards.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/EarlyCSE/guards.ll?rev=268120&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/EarlyCSE/guards.ll (added)
+++ llvm/trunk/test/Transforms/EarlyCSE/guards.ll Fri Apr 29 16:52:58 2016
@@ -0,0 +1,181 @@
+; RUN: opt -S -early-cse < %s | FileCheck %s
+
+declare void @llvm.experimental.guard(i1,...)
+
+define i32 @test0(i32* %ptr, i1 %cond) {
+; We can do store to load forwarding over a guard, since it does not
+; clobber memory
+
+; CHECK-LABEL: @test0(
+; CHECK-NEXT: store i32 40, i32* %ptr
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ]
+; CHECK-NEXT: ret i32 40
+
+ store i32 40, i32* %ptr
+ call void(i1,...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ]
+ %rval = load i32, i32* %ptr
+ ret i32 %rval
+}
+
+define i32 @test1(i32* %val, i1 %cond) {
+; We can CSE loads over a guard, since it does not clobber memory
+
+; CHECK-LABEL: @test1(
+; CHECK-NEXT: %val0 = load i32, i32* %val
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ]
+; CHECK-NEXT: ret i32 0
+
+ %val0 = load i32, i32* %val
+ call void(i1,...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ]
+ %val1 = load i32, i32* %val
+ %rval = sub i32 %val0, %val1
+ ret i32 %rval
+}
+
+define i32 @test2() {
+; Guards on "true" get removed
+
+; CHECK-LABEL: @test2(
+; CHECK-NEXT: ret i32 0
+ call void(i1, ...) @llvm.experimental.guard(i1 true) [ "deopt"() ]
+ ret i32 0
+}
+
+define i32 @test3(i32 %val) {
+; After a guard has executed the condition it was guarding is known to
+; be true.
+
+; CHECK-LABEL: @test3(
+; CHECK-NEXT: %cond0 = icmp slt i32 %val, 40
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond0) [ "deopt"() ]
+; CHECK-NEXT: ret i32 -1
+
+ %cond0 = icmp slt i32 %val, 40
+ call void(i1,...) @llvm.experimental.guard(i1 %cond0) [ "deopt"() ]
+ %cond1 = icmp slt i32 %val, 40
+ call void(i1,...) @llvm.experimental.guard(i1 %cond1) [ "deopt"() ]
+
+ %cond2 = icmp slt i32 %val, 40
+ %rval = sext i1 %cond2 to i32
+ ret i32 %rval
+}
+
+define i32 @test3.unhandled(i32 %val) {
+; After a guard has executed the condition it was guarding is known to
+; be true.
+
+; CHECK-LABEL: @test3.unhandled(
+; CHECK-NEXT: %cond0 = icmp slt i32 %val, 40
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond0) [ "deopt"() ]
+; CHECK-NEXT: %cond1 = icmp sge i32 %val, 40
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond1) [ "deopt"() ]
+; CHECK-NEXT: ret i32 0
+
+; Demonstrates a case we do not yet handle (it is legal to fold %cond2
+; to false)
+ %cond0 = icmp slt i32 %val, 40
+ call void(i1,...) @llvm.experimental.guard(i1 %cond0) [ "deopt"() ]
+ %cond1 = icmp sge i32 %val, 40
+ call void(i1,...) @llvm.experimental.guard(i1 %cond1) [ "deopt"() ]
+ ret i32 0
+}
+
+define i32 @test4(i32 %val, i1 %c) {
+; Same as test3, but with some control flow involved.
+
+; CHECK-LABEL: @test4(
+; CHECK: entry:
+; CHECK-NEXT: %cond0 = icmp slt i32 %val, 40
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond0
+; CHECK-NEXT: br label %bb0
+
+; CHECK: bb0:
+; CHECK-NEXT: %cond2 = icmp ult i32 %val, 200
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond2
+; CHECK-NEXT: br i1 %c, label %left, label %right
+
+; CHECK: left:
+; CHECK-NEXT: ret i32 0
+
+; CHECK: right:
+; CHECK-NEXT: ret i32 20
+
+entry:
+ %cond0 = icmp slt i32 %val, 40
+ call void(i1,...) @llvm.experimental.guard(i1 %cond0) [ "deopt"() ]
+ %cond1 = icmp slt i32 %val, 40
+ call void(i1,...) @llvm.experimental.guard(i1 %cond1) [ "deopt"() ]
+ br label %bb0
+
+bb0:
+ %cond2 = icmp ult i32 %val, 200
+ call void(i1,...) @llvm.experimental.guard(i1 %cond2) [ "deopt"() ]
+ br i1 %c, label %left, label %right
+
+left:
+ %cond3 = icmp ult i32 %val, 200
+ call void(i1,...) @llvm.experimental.guard(i1 %cond3) [ "deopt"() ]
+ ret i32 0
+
+right:
+ ret i32 20
+}
+
+define i32 @test5(i32 %val, i1 %c) {
+; Same as test4, but the %left block has mutliple predecessors.
+
+; CHECK-LABEL: @test5(
+
+; CHECK: entry:
+; CHECK-NEXT: %cond0 = icmp slt i32 %val, 40
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond0
+; CHECK-NEXT: br label %bb0
+
+; CHECK: bb0:
+; CHECK-NEXT: %cond2 = icmp ult i32 %val, 200
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %cond2
+; CHECK-NEXT: br i1 %c, label %left, label %right
+
+; CHECK: left:
+; CHECK-NEXT: br label %right
+
+; CHECK: right:
+; CHECK-NEXT: br label %left
+
+entry:
+ %cond0 = icmp slt i32 %val, 40
+ call void(i1,...) @llvm.experimental.guard(i1 %cond0) [ "deopt"() ]
+ %cond1 = icmp slt i32 %val, 40
+ call void(i1,...) @llvm.experimental.guard(i1 %cond1) [ "deopt"() ]
+ br label %bb0
+
+bb0:
+ %cond2 = icmp ult i32 %val, 200
+ call void(i1,...) @llvm.experimental.guard(i1 %cond2) [ "deopt"() ]
+ br i1 %c, label %left, label %right
+
+left:
+ %cond3 = icmp ult i32 %val, 200
+ call void(i1,...) @llvm.experimental.guard(i1 %cond3) [ "deopt"() ]
+ br label %right
+
+right:
+ br label %left
+}
+
+define void @test6(i1 %c, i32* %ptr) {
+; Check that we do not DSE over calls to @llvm.experimental.guard.
+; Guard intrinsics do _read_ memory, so th call to guard below needs
+; to see the store of 500 to %ptr
+
+; CHECK-LABEL: @test6(
+; CHECK-NEXT: store i32 500, i32* %ptr
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %c) [ "deopt"() ]
+; CHECK-NEXT: store i32 600, i32* %ptr
+
+
+ store i32 500, i32* %ptr
+ call void(i1,...) @llvm.experimental.guard(i1 %c) [ "deopt"() ]
+ store i32 600, i32* %ptr
+ ret void
+}
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