[llvm-commits] [llvm] r122045 - in /llvm/trunk: include/llvm/Support/ConstantRange.h lib/Transforms/Utils/SimplifyCFG.cpp test/Transforms/SimplifyCFG/switch_create.ll
Chris Lattner
sabre at nondot.org
Thu Dec 16 22:20:15 PST 2010
Author: lattner
Date: Fri Dec 17 00:20:15 2010
New Revision: 122045
URL: http://llvm.org/viewvc/llvm-project?rev=122045&view=rev
Log:
improve switch formation to handle small range
comparisons formed by comparisons. For example,
this:
void foo(unsigned x) {
if (x == 0 || x == 1 || x == 3 || x == 4 || x == 6)
bar();
}
compiles into:
_foo: ## @foo
## BB#0: ## %entry
cmpl $6, %edi
ja LBB0_2
## BB#1: ## %entry
movl %edi, %eax
movl $91, %ecx
btq %rax, %rcx
jb LBB0_3
instead of:
_foo: ## @foo
## BB#0: ## %entry
cmpl $2, %edi
jb LBB0_4
## BB#1: ## %switch.early.test
cmpl $6, %edi
ja LBB0_3
## BB#2: ## %switch.early.test
movl %edi, %eax
movl $88, %ecx
btq %rax, %rcx
jb LBB0_4
This catches a bunch of cases in GCC, which look like this:
%804 = load i32* @which_alternative, align 4, !tbaa !0
%805 = icmp ult i32 %804, 2
%806 = icmp eq i32 %804, 3
%or.cond121 = or i1 %805, %806
%807 = icmp eq i32 %804, 4
%or.cond124 = or i1 %or.cond121, %807
br i1 %or.cond124, label %.thread, label %808
turning this into a range comparison.
Modified:
llvm/trunk/include/llvm/Support/ConstantRange.h
llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/trunk/test/Transforms/SimplifyCFG/switch_create.ll
Modified: llvm/trunk/include/llvm/Support/ConstantRange.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/ConstantRange.h?rev=122045&r1=122044&r2=122045&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/ConstantRange.h (original)
+++ llvm/trunk/include/llvm/Support/ConstantRange.h Fri Dec 17 00:20:15 2010
@@ -54,7 +54,7 @@
/// @brief Initialize a range of values explicitly. This will assert out if
/// Lower==Upper and Lower != Min or Max value for its type. It will also
/// assert out if the two APInt's are not the same bit width.
- ConstantRange(const APInt& Lower, const APInt& Upper);
+ ConstantRange(const APInt &Lower, const APInt &Upper);
/// makeICmpRegion - Produce the smallest range that contains all values that
/// might satisfy the comparison specified by Pred when compared to any value
Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=122045&r1=122044&r2=122045&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Fri Dec 17 00:20:15 2010
@@ -28,6 +28,7 @@
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/CFG.h"
+#include "llvm/Support/ConstantRange.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
@@ -305,11 +306,33 @@
// If this is an icmp against a constant, handle this as one of the cases.
if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) {
- if (ICI->getPredicate() == (isEQ ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE))
- if (ConstantInt *C = GetConstantInt(I->getOperand(1), TD)) {
+ if (ConstantInt *C = GetConstantInt(I->getOperand(1), TD)) {
+ if (ICI->getPredicate() == (isEQ ? ICmpInst::ICMP_EQ:ICmpInst::ICMP_NE)) {
Vals.push_back(C);
return I->getOperand(0);
}
+
+ // If we have "x ult 3" comparison, for example, then we can add 0,1,2 to
+ // the set.
+ ConstantRange Span =
+ ConstantRange::makeICmpRegion(ICI->getPredicate(),
+ ConstantRange(C->getValue()));
+
+ // If this is an and/!= check then we want to optimize "x ugt 2" into
+ // x != 0 && x != 1.
+ if (!isEQ)
+ Span = Span.inverse();
+
+ // If there are a ton of values, we don't want to make a ginormous switch.
+ if (Span.getSetSize().getZExtValue() > 8 || Span.isEmptySet() ||
+ // We don't handle wrapped sets yet.
+ Span.isWrappedSet())
+ return 0;
+
+ for (APInt Tmp = Span.getLower(); Tmp != Span.getUpper(); ++Tmp)
+ Vals.push_back(ConstantInt::get(V->getContext(), Tmp));
+ return I->getOperand(0);
+ }
return 0;
}
Modified: llvm/trunk/test/Transforms/SimplifyCFG/switch_create.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/switch_create.ll?rev=122045&r1=122044&r2=122045&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/switch_create.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/switch_create.ll Fri Dec 17 00:20:15 2010
@@ -351,4 +351,73 @@
ret void
; CHECK: @test12
-}
\ No newline at end of file
+}
+
+; test13 - handle switch formation with ult.
+define void @test13(i32 %x) nounwind ssp noredzone {
+entry:
+ %cmp = icmp ult i32 %x, 2
+ br i1 %cmp, label %if.then, label %lor.lhs.false3
+
+lor.lhs.false3: ; preds = %lor.lhs.false
+ %cmp5 = icmp eq i32 %x, 3
+ br i1 %cmp5, label %if.then, label %lor.lhs.false6
+
+lor.lhs.false6: ; preds = %lor.lhs.false3
+ %cmp8 = icmp eq i32 %x, 4
+ br i1 %cmp8, label %if.then, label %lor.lhs.false9
+
+lor.lhs.false9: ; preds = %lor.lhs.false6
+ %cmp11 = icmp eq i32 %x, 6
+ br i1 %cmp11, label %if.then, label %if.end
+
+if.then: ; preds = %lor.lhs.false9, %lor.lhs.false6, %lor.lhs.false3, %lor.lhs.false, %entry
+ call void @foo1() noredzone
+ br label %if.end
+
+if.end: ; preds = %if.then, %lor.lhs.false9
+ ret void
+; CHECK: @test13
+; CHECK: switch i32 %x, label %if.end [
+; CHECK: i32 6, label %if.then
+; CHECK: i32 4, label %if.then
+; CHECK: i32 3, label %if.then
+; CHECK: i32 1, label %if.then
+; CHECK: i32 0, label %if.then
+; CHECK: ]
+}
+
+; test14 - handle switch formation with ult.
+define void @test14(i32 %x) nounwind ssp noredzone {
+entry:
+ %cmp = icmp ugt i32 %x, 2
+ br i1 %cmp, label %lor.lhs.false3, label %if.then
+
+lor.lhs.false3: ; preds = %lor.lhs.false
+ %cmp5 = icmp ne i32 %x, 3
+ br i1 %cmp5, label %lor.lhs.false6, label %if.then
+
+lor.lhs.false6: ; preds = %lor.lhs.false3
+ %cmp8 = icmp ne i32 %x, 4
+ br i1 %cmp8, label %lor.lhs.false9, label %if.then
+
+lor.lhs.false9: ; preds = %lor.lhs.false6
+ %cmp11 = icmp ne i32 %x, 6
+ br i1 %cmp11, label %if.end, label %if.then
+
+if.then: ; preds = %lor.lhs.false9, %lor.lhs.false6, %lor.lhs.false3, %lor.lhs.false, %entry
+ call void @foo1() noredzone
+ br label %if.end
+
+if.end: ; preds = %if.then, %lor.lhs.false9
+ ret void
+; CHECK: @test14
+; CHECK: switch i32 %x, label %if.end [
+; CHECK: i32 6, label %if.then
+; CHECK: i32 4, label %if.then
+; CHECK: i32 3, label %if.then
+; CHECK: i32 1, label %if.then
+; CHECK: i32 0, label %if.then
+; CHECK: ]
+}
+
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