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7e1b2bd8a7
Add profitability checks for modifying counted loops to use the mtctr instruction. The latency of mtctr is only justified if there are more than 4 comparisons that will be removed as a result. Usually counted loops are formed relatively early and before unrolling, so most low trip count loops often don't survive. However we want to ensure that if they do, we do not mistakenly update them to mtctr loops. Use CodeMetrics to ensure we are only doing this for small loops with small trip counts. Differential Revision: https://reviews.llvm.org/D38212 llvm-svn: 315592
117 lines
3.9 KiB
LLVM
117 lines
3.9 KiB
LLVM
; RUN: llc < %s -mtriple=powerpc64le-unknown-linux-gnu -verify-machineinstrs -mcpu=pwr8 | FileCheck %s
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; RUN: llc < %s -mtriple=powerpc64le-unknown-linux-gnu -verify-machineinstrs -mcpu=a2q | FileCheck %s
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; Verify that we do NOT generate the mtctr instruction for loop trip counts < 4
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; The latency of the mtctr is only justified if there are more than 4 comparisons that are removed as a result.
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@a = common local_unnamed_addr global i32 0, align 4
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@arr = common local_unnamed_addr global [5 x i32] zeroinitializer, align 4
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; Function Attrs: norecurse nounwind readonly
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define signext i32 @testTripCount2(i32 signext %a) {
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; CHECK-LABEL: testTripCount2:
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; CHECK-NOT: mtctr
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; CHECK: blr
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entry:
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br label %for.body
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for.cond.cleanup: ; preds = %for.body
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ret i32 %add
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for.body: ; preds = %entry, %for.body
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%indvars.iv = phi i64 [ 1, %entry ], [ %indvars.iv.next, %for.body ]
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%Sum.05 = phi i32 [ 0, %entry ], [ %add, %for.body ]
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%arrayidx = getelementptr inbounds [5 x i32], [5 x i32]* @arr, i64 0, i64 %indvars.iv
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%0 = load i32, i32* %arrayidx, align 4
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%add = add nsw i32 %0, %Sum.05
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%indvars.iv.next = add nsw i64 %indvars.iv, -1
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%tobool = icmp eq i64 %indvars.iv, 0
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br i1 %tobool, label %for.cond.cleanup, label %for.body
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}
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; Function Attrs: norecurse nounwind readonly
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define signext i32 @testTripCount3(i32 signext %a) {
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; CHECK-LABEL: testTripCount3:
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; CHECK-NOT: mtctr
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; CHECK: blr
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entry:
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br label %for.body
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for.cond.cleanup: ; preds = %for.body
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ret i32 %add
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for.body: ; preds = %entry, %for.body
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%indvars.iv = phi i64 [ 2, %entry ], [ %indvars.iv.next, %for.body ]
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%Sum.05 = phi i32 [ 0, %entry ], [ %add, %for.body ]
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%arrayidx = getelementptr inbounds [5 x i32], [5 x i32]* @arr, i64 0, i64 %indvars.iv
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%0 = load i32, i32* %arrayidx, align 4
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%add = add nsw i32 %0, %Sum.05
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%indvars.iv.next = add nsw i64 %indvars.iv, -1
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%tobool = icmp eq i64 %indvars.iv, 0
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br i1 %tobool, label %for.cond.cleanup, label %for.body
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}
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; Function Attrs: norecurse nounwind readonly
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define signext i32 @testTripCount4(i32 signext %a) {
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; CHECK-LABEL: testTripCount4:
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; CHECK: mtctr
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; CHECK: bdnz
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entry:
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br label %for.body
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for.cond.cleanup: ; preds = %for.body
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ret i32 %add
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for.body: ; preds = %entry, %for.body
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%indvars.iv = phi i64 [ 3, %entry ], [ %indvars.iv.next, %for.body ]
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%Sum.05 = phi i32 [ 0, %entry ], [ %add, %for.body ]
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%arrayidx = getelementptr inbounds [5 x i32], [5 x i32]* @arr, i64 0, i64 %indvars.iv
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%0 = load i32, i32* %arrayidx, align 4
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%add = add nsw i32 %0, %Sum.05
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%indvars.iv.next = add nsw i64 %indvars.iv, -1
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%tobool = icmp eq i64 %indvars.iv, 0
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br i1 %tobool, label %for.cond.cleanup, label %for.body
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}
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; Function Attrs: norecurse nounwind
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define signext i32 @testTripCount2NonSmallLoop() {
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; CHECK-LABEL: testTripCount2NonSmallLoop:
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; CHECK: mtctr
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; CHECK: blr
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entry:
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%.pre = load i32, i32* @a, align 4
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br label %for.body
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for.body: ; preds = %entry, %if.end
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%0 = phi i32 [ %.pre, %entry ], [ %1, %if.end ]
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%dec4 = phi i32 [ 1, %entry ], [ %dec, %if.end ]
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%b.03 = phi i8 [ 0, %entry ], [ %b.1, %if.end ]
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%tobool1 = icmp eq i32 %0, 0
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br i1 %tobool1, label %if.end, label %if.then
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if.then: ; preds = %for.body
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store i32 2, i32* @a, align 4
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br label %if.end
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if.end: ; preds = %for.body, %if.then
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%1 = phi i32 [ 2, %if.then ], [ 0, %for.body ]
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%b.1 = phi i8 [ 2, %if.then ], [ %b.03, %for.body ]
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%dec = add nsw i32 %dec4, -1
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%tobool = icmp eq i32 %dec4, 0
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br i1 %tobool, label %for.end, label %for.body
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for.end: ; preds = %if.end
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%conv = zext i8 %b.1 to i32
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ret i32 %conv
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}
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