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[LVI] Disable at-use reasoning across phi nodes (PR60629)
For phi nodes, while we can make use of the edge condition for the incoming value, we shouldn't look past the phi node to look for further conditions, because we might be reasoning about values from two different cycle iterations (which will have the same SSA value). To handle this more specifically we would have to detect cycles, and there doesn't seem to be any motivating case for that at this point.
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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py | ||
; RUN: opt -passes=correlated-propagation -S %s | FileCheck %s | ||
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; Check that shift is not removed by CVP because of incorrect range returned by LVI::getConstantRangeAtUse. | ||
; https://github.com/llvm/llvm-project/issues/60629 | ||
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define i32 @test(i32 %arg) { | ||
; CHECK-LABEL: @test( | ||
; CHECK-NEXT: entry: | ||
; CHECK-NEXT: br label [[LOOP:%.*]] | ||
; CHECK: loop: | ||
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 127, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[DO_SHIFT:%.*]] ] | ||
; CHECK-NEXT: [[SHIFTED_IV:%.*]] = phi i32 [ 0, [[ENTRY]] ], [ [[SHIFT:%.*]], [[DO_SHIFT]] ] | ||
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1 | ||
; CHECK-NEXT: [[LOOP_COND:%.*]] = icmp sgt i32 [[IV]], 127 | ||
; CHECK-NEXT: br i1 [[LOOP_COND]], label [[EXIT:%.*]], label [[DO_SHIFT]] | ||
; CHECK: do.shift: | ||
; CHECK-NEXT: [[SHIFT]] = ashr i32 [[IV]], [[ARG:%.*]] | ||
; CHECK-NEXT: br label [[LOOP]] | ||
; CHECK: bb1: | ||
; CHECK-NEXT: br label [[EXIT]] | ||
; CHECK: exit: | ||
; CHECK-NEXT: [[RETVAL:%.*]] = phi i32 [ 0, [[BB1:%.*]] ], [ [[SHIFTED_IV]], [[LOOP]] ] | ||
; CHECK-NEXT: ret i32 [[RETVAL]] | ||
; | ||
entry: | ||
br label %loop | ||
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loop: ; preds = %do.shift, %entry | ||
%iv = phi i32 [ 127, %entry ], [ %iv.next, %do.shift ] | ||
%shifted.iv = phi i32 [ 0, %entry ], [ %shift, %do.shift ] | ||
%iv.next = add i32 %iv, 1 | ||
%loop_cond = icmp sgt i32 %iv, 127 | ||
br i1 %loop_cond, label %exit, label %do.shift | ||
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do.shift: ; preds = %loop | ||
%shift = ashr i32 %iv, %arg | ||
br label %loop | ||
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bb1: ; No predecessors! | ||
br label %exit | ||
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exit: ; preds = %loop, %bb1 | ||
%retval = phi i32 [ 0, %bb1 ], [ %shifted.iv, %loop ] | ||
ret i32 %retval | ||
} |