[PATCH] D139289: [SCCP] Propagate equality or inequality state of a not-constant

[luxufan via Phabricator via llvm-commits]

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The equality or inequality state of a not-constant can also be used
to do constant propagation. For example,

  define i32 @equal_not_constant(ptr noundef %p, ptr noundef %q) {
  entry:
    %cmp = icmp ne ptr %p, null
    br i1 %cmp, label %if.then, label %if.end
  
  if.then:                                          ; preds = %entry
    %cmp.then = icmp eq ptr %p, %q
    br i1 %cmp.then, label %if.then1, label %if.end
  
  if.then1:                                         ; preds = %if.then
    %cmp.then1 = icmp ne ptr %q, null
    call void @use(i1 %cmp.then1)
    br label %if.end
  
  if.end:
    ret i32 0
  }

In this case, we can fold `%cmp.then1` as `true`.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D139289

Files:
  llvm/lib/Transforms/Utils/SCCPSolver.cpp
  llvm/test/Transforms/SCCP/conditions-ranges.ll

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