[llvm] r228829 - [TTI] Improved cost heuristic for cttz/ctlz calls.
Andrea Di Biagio
Andrea_DiBiagio at sn.scee.net
Wed Feb 11 06:22:18 PST 2015
Author: adibiagio
Date: Wed Feb 11 08:22:18 2015
New Revision: 228829
URL: http://llvm.org/viewvc/llvm-project?rev=228829&view=rev
Log:
[TTI] Improved cost heuristic for cttz/ctlz calls.
This patch is a follow-up of r228826 (see code-review: D7506).
Now that SimplifyCFG uses TargetTransformInfo for cost analysis, we
have to fix the cost heuristic for intrinsic calls to cttz/ctlz.
This patch defines method 'getIntrinsicCost' in BasicTTIImpl: now, BasicTTIImpl
queries TLI to check if a call to cttz/ctlz is cheap for the target.
Added test cases in Transforms/SimplifyCFG/X86 to verify that on x86,
SimplifyCFG only speculates a call to cttz/ctlz if it is cheap.
Differential Revision: http://reviews.llvm.org/D7554
Added:
llvm/trunk/test/Transforms/SimplifyCFG/X86/speculate-cttz-ctlz.ll
Modified:
llvm/trunk/include/llvm/CodeGen/BasicTTIImpl.h
llvm/trunk/test/Transforms/SimplifyCFG/SpeculativeExec.ll
Modified: llvm/trunk/include/llvm/CodeGen/BasicTTIImpl.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/BasicTTIImpl.h?rev=228829&r1=228828&r2=228829&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/BasicTTIImpl.h (original)
+++ llvm/trunk/include/llvm/CodeGen/BasicTTIImpl.h Wed Feb 11 08:22:18 2015
@@ -150,6 +150,28 @@ public:
return getTLI()->isTypeLegal(VT);
}
+ unsigned getIntrinsicCost(Intrinsic::ID IID, Type *RetTy,
+ ArrayRef<const Value *> Arguments) {
+ return BaseT::getIntrinsicCost(IID, RetTy, Arguments);
+ }
+
+ unsigned getIntrinsicCost(Intrinsic::ID IID, Type *RetTy,
+ ArrayRef<Type *> ParamTys) {
+ if (IID == Intrinsic::cttz) {
+ if (getTLI()->isCheapToSpeculateCttz())
+ return TargetTransformInfo::TCC_Basic;
+ return TargetTransformInfo::TCC_Expensive;
+ }
+
+ if (IID == Intrinsic::ctlz) {
+ if (getTLI()->isCheapToSpeculateCtlz())
+ return TargetTransformInfo::TCC_Basic;
+ return TargetTransformInfo::TCC_Expensive;
+ }
+
+ return BaseT::getIntrinsicCost(IID, RetTy, ParamTys);
+ }
+
unsigned getJumpBufAlignment() { return getTLI()->getJumpBufAlignment(); }
unsigned getJumpBufSize() { return getTLI()->getJumpBufSize(); }
Modified: llvm/trunk/test/Transforms/SimplifyCFG/SpeculativeExec.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/SpeculativeExec.ll?rev=228829&r1=228828&r2=228829&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/SpeculativeExec.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/SpeculativeExec.ll Wed Feb 11 08:22:18 2015
@@ -28,22 +28,6 @@ bb3: ; preds = %bb2, %entry
ret i32 %tmp5
}
-declare i8 @llvm.cttz.i8(i8, i1)
-
-define i8 @test2(i8 %a) {
-; CHECK-LABEL: @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
-}
-
define i8* @test4(i1* %dummy, i8* %a, i8* %b) {
; Test that we don't speculate an arbitrarily large number of unfolded constant
; expressions.
Added: llvm/trunk/test/Transforms/SimplifyCFG/X86/speculate-cttz-ctlz.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/X86/speculate-cttz-ctlz.ll?rev=228829&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/X86/speculate-cttz-ctlz.ll (added)
+++ llvm/trunk/test/Transforms/SimplifyCFG/X86/speculate-cttz-ctlz.ll Wed Feb 11 08:22:18 2015
@@ -0,0 +1,141 @@
+; RUN: opt -S -simplifycfg -mtriple=x86_64-unknown-unknown -mattr=+bmi < %s | FileCheck %s --check-prefix=ALL --check-prefix=BMI
+; RUN: opt -S -simplifycfg -mtriple=x86_64-unknown-unknown -mattr=+lzcnt < %s | FileCheck %s --check-prefix=ALL --check-prefix=LZCNT
+; RUN: opt -S -simplifycfg -mtriple=x86_64-unknown-unknown < %s | FileCheck %s --check-prefix=ALL --check-prefix=GENERIC
+
+
+define i64 @test1(i64 %A) {
+; ALL-LABEL: @test1(
+; ALL: [[COND:%[A-Za-z0-9]+]] = icmp eq i64 %A, 0
+; ALL: [[CTLZ:%[A-Za-z0-9]+]] = tail call i64 @llvm.ctlz.i64(i64 %A, i1 true)
+; LZCNT-NEXT: select i1 [[COND]], i64 64, i64 [[CTLZ]]
+; BMI-NOT: select
+; GENERIC-NOT: select
+; ALL: ret
+entry:
+ %tobool = icmp eq i64 %A, 0
+ br i1 %tobool, label %cond.end, label %cond.true
+
+cond.true: ; preds = %entry
+ %0 = tail call i64 @llvm.ctlz.i64(i64 %A, i1 true)
+ br label %cond.end
+
+cond.end: ; preds = %entry, %cond.true
+ %cond = phi i64 [ %0, %cond.true ], [ 64, %entry ]
+ ret i64 %cond
+}
+
+define i32 @test2(i32 %A) {
+; ALL-LABEL: @test2(
+; ALL: [[COND:%[A-Za-z0-9]+]] = icmp eq i32 %A, 0
+; ALL: [[CTLZ:%[A-Za-z0-9]+]] = tail call i32 @llvm.ctlz.i32(i32 %A, i1 true)
+; LZCNT-NEXT: select i1 [[COND]], i32 32, i32 [[CTLZ]]
+; BMI-NOT: select
+; GENERIC-NOT: select
+; ALL: ret
+entry:
+ %tobool = icmp eq i32 %A, 0
+ br i1 %tobool, label %cond.end, label %cond.true
+
+cond.true: ; preds = %entry
+ %0 = tail call i32 @llvm.ctlz.i32(i32 %A, i1 true)
+ br label %cond.end
+
+cond.end: ; preds = %entry, %cond.true
+ %cond = phi i32 [ %0, %cond.true ], [ 32, %entry ]
+ ret i32 %cond
+}
+
+
+define signext i16 @test3(i16 signext %A) {
+; ALL-LABEL: @test3(
+; ALL: [[COND:%[A-Za-z0-9]+]] = icmp eq i16 %A, 0
+; ALL: [[CTLZ:%[A-Za-z0-9]+]] = tail call i16 @llvm.ctlz.i16(i16 %A, i1 true)
+; LZCNT-NEXT: select i1 [[COND]], i16 16, i16 [[CTLZ]]
+; BMI-NOT: select
+; GENERIC-NOT: select
+; ALL: ret
+entry:
+ %tobool = icmp eq i16 %A, 0
+ br i1 %tobool, label %cond.end, label %cond.true
+
+cond.true: ; preds = %entry
+ %0 = tail call i16 @llvm.ctlz.i16(i16 %A, i1 true)
+ br label %cond.end
+
+cond.end: ; preds = %entry, %cond.true
+ %cond = phi i16 [ %0, %cond.true ], [ 16, %entry ]
+ ret i16 %cond
+}
+
+
+define i64 @test1b(i64 %A) {
+; ALL-LABEL: @test1b(
+; ALL: [[COND:%[A-Za-z0-9]+]] = icmp eq i64 %A, 0
+; ALL: [[CTTZ:%[A-Za-z0-9]+]] = tail call i64 @llvm.cttz.i64(i64 %A, i1 true)
+; BMI-NEXT: select i1 [[COND]], i64 64, i64 [[CTTZ]]
+; LZCNT-NOT: select
+; GENERIC-NOT: select
+; ALL: ret
+entry:
+ %tobool = icmp eq i64 %A, 0
+ br i1 %tobool, label %cond.end, label %cond.true
+
+cond.true: ; preds = %entry
+ %0 = tail call i64 @llvm.cttz.i64(i64 %A, i1 true)
+ br label %cond.end
+
+cond.end: ; preds = %entry, %cond.true
+ %cond = phi i64 [ %0, %cond.true ], [ 64, %entry ]
+ ret i64 %cond
+}
+
+
+define i32 @test2b(i32 %A) {
+; ALL-LABEL: @test2b(
+; ALL: [[COND:%[A-Za-z0-9]+]] = icmp eq i32 %A, 0
+; ALL: [[CTTZ:%[A-Za-z0-9]+]] = tail call i32 @llvm.cttz.i32(i32 %A, i1 true)
+; BMI-NEXT: select i1 [[COND]], i32 32, i32 [[CTTZ]]
+; LZCNT-NOT: select
+; GENERIC-NOT: select
+; ALL: ret
+entry:
+ %tobool = icmp eq i32 %A, 0
+ br i1 %tobool, label %cond.end, label %cond.true
+
+cond.true: ; preds = %entry
+ %0 = tail call i32 @llvm.cttz.i32(i32 %A, i1 true)
+ br label %cond.end
+
+cond.end: ; preds = %entry, %cond.true
+ %cond = phi i32 [ %0, %cond.true ], [ 32, %entry ]
+ ret i32 %cond
+}
+
+
+define signext i16 @test3b(i16 signext %A) {
+; ALL-LABEL: @test3b(
+; ALL: [[COND:%[A-Za-z0-9]+]] = icmp eq i16 %A, 0
+; ALL: [[CTTZ:%[A-Za-z0-9]+]] = tail call i16 @llvm.cttz.i16(i16 %A, i1 true)
+; BMI-NEXT: select i1 [[COND]], i16 16, i16 [[CTTZ]]
+; LZCNT-NOT: select
+; GENERIC-NOT: select
+; ALL: ret
+entry:
+ %tobool = icmp eq i16 %A, 0
+ br i1 %tobool, label %cond.end, label %cond.true
+
+cond.true: ; preds = %entry
+ %0 = tail call i16 @llvm.cttz.i16(i16 %A, i1 true)
+ br label %cond.end
+
+cond.end: ; preds = %entry, %cond.true
+ %cond = phi i16 [ %0, %cond.true ], [ 16, %entry ]
+ ret i16 %cond
+}
+
+declare i64 @llvm.ctlz.i64(i64, i1)
+declare i32 @llvm.ctlz.i32(i32, i1)
+declare i16 @llvm.ctlz.i16(i16, i1)
+declare i64 @llvm.cttz.i64(i64, i1)
+declare i32 @llvm.cttz.i32(i32, i1)
+declare i16 @llvm.cttz.i16(i16, i1)
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