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39f379d037
This patch just uses a peephole test for "add; compare; branch" sequences within a single block. The IR optimizers already convert loops to decrement-and-branch-on-nonzero form in some cases, so even this simplistic test triggers many times during a clang bootstrap and projects/test-suite run. It looks like there are still cases where we need to more strongly prefer branches on nonzero though. E.g. I saw a case where a loop that started out with a check for 0 ended up with a check for -1. I'll try to look at that sometime. I ended up adding the Reference class because MachineInstr::readsRegister() doesn't check for subregisters (by design, as far as I could tell). llvm-svn: 187723
125 lines
2.9 KiB
LLVM
125 lines
2.9 KiB
LLVM
; Test loop tuning.
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;
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; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z10 | FileCheck %s
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; Test that strength reduction is applied to addresses with a scale factor,
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; but that indexed addressing can still be used.
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define void @f1(i32 *%dest, i32 %a) {
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; CHECK-LABEL: f1:
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; CHECK-NOT: sllg
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; CHECK: st %r3, 0({{%r[1-5],%r[1-5]}})
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; CHECK: br %r14
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entry:
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br label %loop
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loop:
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%index = phi i64 [ 0, %entry ], [ %next, %loop ]
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%ptr = getelementptr i32 *%dest, i64 %index
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store i32 %a, i32 *%ptr
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%next = add i64 %index, 1
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%cmp = icmp ne i64 %next, 100
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br i1 %cmp, label %loop, label %exit
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exit:
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ret void
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}
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; Test a loop that should be converted into dbr form and then use BRCT.
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define void @f2(i32 *%src, i32 *%dest) {
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; CHECK-LABEL: f2:
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; CHECK: lhi [[REG:%r[0-5]]], 100
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; CHECK: [[LABEL:\.[^:]*]]:{{.*}} %loop
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; CHECK: brct [[REG]], [[LABEL]]
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; CHECK: br %r14
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entry:
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br label %loop
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loop:
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%count = phi i32 [ 0, %entry ], [ %next, %loop.next ]
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%next = add i32 %count, 1
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%val = load volatile i32 *%src
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%cmp = icmp eq i32 %val, 0
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br i1 %cmp, label %loop.next, label %loop.store
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loop.store:
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%add = add i32 %val, 1
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store volatile i32 %add, i32 *%dest
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br label %loop.next
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loop.next:
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%cont = icmp ne i32 %next, 100
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br i1 %cont, label %loop, label %exit
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exit:
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ret void
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}
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; Like f2, but for BRCTG.
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define void @f3(i64 *%src, i64 *%dest) {
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; CHECK-LABEL: f3:
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; CHECK: lghi [[REG:%r[0-5]]], 100
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; CHECK: [[LABEL:\.[^:]*]]:{{.*}} %loop
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; CHECK: brctg [[REG]], [[LABEL]]
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; CHECK: br %r14
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entry:
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br label %loop
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loop:
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%count = phi i64 [ 0, %entry ], [ %next, %loop.next ]
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%next = add i64 %count, 1
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%val = load volatile i64 *%src
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%cmp = icmp eq i64 %val, 0
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br i1 %cmp, label %loop.next, label %loop.store
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loop.store:
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%add = add i64 %val, 1
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store volatile i64 %add, i64 *%dest
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br label %loop.next
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loop.next:
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%cont = icmp ne i64 %next, 100
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br i1 %cont, label %loop, label %exit
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exit:
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ret void
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}
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; Test a loop with a 64-bit decremented counter in which the 32-bit
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; low part of the counter is used after the decrement. This is an example
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; of a subregister use being the only thing that blocks a conversion to BRCTG.
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define void @f4(i32 *%src, i32 *%dest, i64 *%dest2, i64 %count) {
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; CHECK-LABEL: f4:
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; CHECK: aghi [[REG:%r[0-5]]], -1
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; CHECK: lr [[REG2:%r[0-5]]], [[REG]]
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; CHECK: stg [[REG2]],
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; CHECK: jne {{\..*}}
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; CHECK: br %r14
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entry:
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br label %loop
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loop:
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%left = phi i64 [ %count, %entry ], [ %next, %loop.next ]
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store volatile i64 %left, i64 *%dest2
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%val = load volatile i32 *%src
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%cmp = icmp eq i32 %val, 0
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br i1 %cmp, label %loop.next, label %loop.store
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loop.store:
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%add = add i32 %val, 1
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store volatile i32 %add, i32 *%dest
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br label %loop.next
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loop.next:
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%next = add i64 %left, -1
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%ext = zext i32 %val to i64
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%shl = shl i64 %ext, 32
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%and = and i64 %next, 4294967295
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%or = or i64 %shl, %and
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store volatile i64 %or, i64 *%dest2
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%cont = icmp ne i64 %next, 0
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br i1 %cont, label %loop, label %exit
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exit:
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ret void
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}
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