ab12bba0aa
See the following case:
```
define i8 @src1(i8 %x) {
entry:
%cmp = icmp eq i8 %x, -1
br i1 %cmp, label %exit, label %if.then
if.then:
%inc = add nuw nsw i8 %x, 1
br label %exit
exit:
%retval = phi i8 [ %inc, %if.then ], [ -1, %entry ]
ret i8 %retval
}
define i8 @tgt1(i8 %x) {
entry:
%inc = add nuw nsw i8 %x, 1
%0 = icmp eq i8 %inc, 0
br i1 %0, label %exit, label %if.then
if.then: ; preds = %entry
br label %exit
exit: ; preds = %if.then, %entry
%retval = phi i8 [ %inc, %if.then ], [ -1, %entry ]
ret i8 %retval
}
```
`optimizeBranch` converts `icmp eq X, -1` into cmp to zero on RISC-V and
hoists the add into the entry block. Poison-generating flags should be
dropped as they don't still hold.
Proof: https://alive2.llvm.org/ce/z/sP7mvK
Fixes https://github.com/llvm/llvm-project/issues/90380
81 lines
2.3 KiB
LLVM
81 lines
2.3 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
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; RUN: opt -codegenprepare -S -mtriple=riscv64 < %s | FileCheck %s
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define i8 @hoist_add(i8 %x) {
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; CHECK-LABEL: define i8 @hoist_add(
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; CHECK-SAME: i8 [[X:%.*]]) {
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[INC:%.*]] = add i8 [[X]], 1
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; CHECK-NEXT: [[TMP0:%.*]] = icmp eq i8 [[INC]], 0
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; CHECK-NEXT: br i1 [[TMP0]], label [[EXIT:%.*]], label [[IF_THEN:%.*]]
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; CHECK: if.then:
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; CHECK-NEXT: br label [[EXIT]]
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; CHECK: exit:
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; CHECK-NEXT: [[RETVAL:%.*]] = phi i8 [ [[INC]], [[IF_THEN]] ], [ -1, [[ENTRY:%.*]] ]
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; CHECK-NEXT: ret i8 [[RETVAL]]
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;
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entry:
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%cmp = icmp eq i8 %x, -1
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br i1 %cmp, label %exit, label %if.then
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if.then:
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%inc = add nuw nsw i8 %x, 1
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br label %exit
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exit:
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%retval = phi i8 [ %inc, %if.then ], [ -1, %entry ]
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ret i8 %retval
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}
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define i8 @hoist_lshr(i8 %x) {
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; CHECK-LABEL: define i8 @hoist_lshr(
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; CHECK-SAME: i8 [[X:%.*]]) {
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[INC:%.*]] = lshr i8 [[X]], 3
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; CHECK-NEXT: [[TMP0:%.*]] = icmp eq i8 [[INC]], 0
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; CHECK-NEXT: br i1 [[TMP0]], label [[EXIT:%.*]], label [[IF_THEN:%.*]]
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; CHECK: if.then:
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; CHECK-NEXT: br label [[EXIT]]
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; CHECK: exit:
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; CHECK-NEXT: [[RETVAL:%.*]] = phi i8 [ [[INC]], [[IF_THEN]] ], [ -1, [[ENTRY:%.*]] ]
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; CHECK-NEXT: ret i8 [[RETVAL]]
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;
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entry:
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%cmp = icmp ult i8 %x, 8
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br i1 %cmp, label %exit, label %if.then
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if.then:
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%inc = lshr exact i8 %x, 3
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br label %exit
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exit:
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%retval = phi i8 [ %inc, %if.then ], [ -1, %entry ]
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ret i8 %retval
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}
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define i8 @nomove_add(i8 %x) {
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; CHECK-LABEL: define i8 @nomove_add(
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; CHECK-SAME: i8 [[X:%.*]]) {
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[INC:%.*]] = add i8 [[X]], 1
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; CHECK-NEXT: [[TMP0:%.*]] = icmp eq i8 [[INC]], 0
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; CHECK-NEXT: br i1 [[TMP0]], label [[EXIT:%.*]], label [[IF_THEN:%.*]]
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; CHECK: if.then:
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; CHECK-NEXT: br label [[EXIT]]
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; CHECK: exit:
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; CHECK-NEXT: [[RETVAL:%.*]] = phi i8 [ [[INC]], [[IF_THEN]] ], [ -1, [[ENTRY:%.*]] ]
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; CHECK-NEXT: ret i8 [[RETVAL]]
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;
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entry:
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%inc = add nuw nsw i8 %x, 1
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%cmp = icmp eq i8 %x, -1
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br i1 %cmp, label %exit, label %if.then
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if.then:
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br label %exit
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exit:
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%retval = phi i8 [ %inc, %if.then ], [ -1, %entry ]
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ret i8 %retval
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}
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