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3fdcf4e64c
If a loop is not rotated (for example when optimizing for size), the latch is not the backedge. If we promote an expression to post-inc form, we not only increase register pressure and add a COPY for that IV expression but for all IVs!
Motivating testcase:
void f(float *a, float *b, float *c, int n) {
while (n-- > 0)
*c++ = *a++ + *b++;
}
It's imperative that the pointer increments be located in the latch block and not the header block; if not, we cannot use post-increment loads and stores and we have to keep both the post-inc and pre-inc values around until the end of the latch which bloats register usage.
llvm-svn: 278658
67 lines
2.4 KiB
LLVM
67 lines
2.4 KiB
LLVM
; RUN: llc -march=hexagon -mcpu=hexagonv5 < %s | FileCheck %s
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;
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; Generate loop1 instruction for double loop sequence.
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; CHECK: loop1(.LBB{{.}}_{{.}}, #100)
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; CHECK: loop0(.LBB{{.}}_{{.}}, #100)
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; CHECK: endloop0
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; CHECK: endloop1
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define i32 @main() #0 {
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entry:
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%array = alloca [100 x i32], align 8
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%doublearray = alloca [100 x [100 x i32]], align 8
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%0 = bitcast [100 x i32]* %array to i8*
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call void @llvm.lifetime.start(i64 400, i8* %0) #1
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%1 = bitcast [100 x [100 x i32]]* %doublearray to i8*
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call void @llvm.lifetime.start(i64 40000, i8* %1) #1
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%arrayidx1 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* %doublearray, i32 0, i32 10, i32 10
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%arrayidx2.gep = getelementptr [100 x i32], [100 x i32]* %array, i32 0, i32 0
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br label %for.body
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for.body:
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%2 = phi i32 [ undef, %entry ], [ %.pre, %for.body.for.body_crit_edge ]
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%sum.031 = phi i32 [ undef, %entry ], [ %add, %for.body.for.body_crit_edge ]
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%arrayidx2.phi = phi i32* [ %arrayidx2.gep, %entry ], [ %arrayidx2.inc, %for.body.for.body_crit_edge ]
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%i.030 = phi i32 [ 1, %entry ], [ %phitmp, %for.body.for.body_crit_edge ]
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%add = add nsw i32 %2, %sum.031
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%exitcond33 = icmp eq i32 %i.030, 100
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%arrayidx2.inc = getelementptr i32, i32* %arrayidx2.phi, i32 1
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br i1 %exitcond33, label %for.cond7.preheader.preheader, label %for.body.for.body_crit_edge
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for.cond7.preheader.preheader:
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br label %for.cond7.preheader
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for.body.for.body_crit_edge:
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%.pre = load i32, i32* %arrayidx2.inc, align 4
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%phitmp = add i32 %i.030, 1
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br label %for.body
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for.cond7.preheader:
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%i.129 = phi i32 [ %inc16, %for.inc15 ], [ 0, %for.cond7.preheader.preheader ]
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br label %for.body9
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for.body9:
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%j.028 = phi i32 [ 0, %for.cond7.preheader ], [ %inc13, %for.body9 ]
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%arrayidx11 = getelementptr inbounds [100 x [100 x i32]], [100 x [100 x i32]]* %doublearray, i32 0, i32 %i.129, i32 %j.028
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store i32 %add, i32* %arrayidx11, align 4
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%inc13 = add nsw i32 %j.028, 1
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%exitcond = icmp eq i32 %inc13, 100
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br i1 %exitcond, label %for.inc15, label %for.body9
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for.inc15:
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%inc16 = add nsw i32 %i.129, 1
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%exitcond32 = icmp eq i32 %inc16, 100
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br i1 %exitcond32, label %for.end17, label %for.cond7.preheader
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for.end17:
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%3 = load i32, i32* %arrayidx1, align 8
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call void @llvm.lifetime.end(i64 40000, i8* %1) #1
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call void @llvm.lifetime.end(i64 400, i8* %0) #1
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ret i32 %3
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}
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declare void @llvm.lifetime.start(i64, i8* nocapture) #1
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declare void @llvm.lifetime.end(i64, i8* nocapture) #1
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