[PATCH] D44421: [InstSimplify] [NFC] Add tests for peeking through unsigned FP casts for sign compares (PR36682)

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added inline comments.


================
Comment at: llvm/trunk/test/Transforms/InstSimplify/cast-unsigned-icmp-cmp-0.ll:2-5
+; RUN: opt < %s -instcombine -instsimplify -S | FileCheck %s
+
+; NOTE: we run instcombine first,
+; to make sure that it does *NOT* drop uitofp+bitcast here.
----------------
lebedev.ri wrote:
> spatel wrote:
> > Sorry - I didn't catch this before. Why are we doing anything with -instcombine here? We should only be running -instsimplify on this file.
> You commented on the explanation note :)
> )I moved it here from the next diff before commit, should have done that earlier)
Uhm, yeah, i was thinking of something else, that instcombine transform would not be valid anyway:
```
$ ~/src/alive-nj/run.py /tmp/slt.txt 
----------                                                                      
Name: slt
  %f   = uitofp i32 %i to float
  %b   = bitcast float %f to i32
  %cmp = icmp slt i32 %b, 0
=>
  %cmp = icmp slt i32 %i, 0

ERROR: Mismatch in values for i1 %cmp                                           

Example:
  i32 %i = 0x80000000 (2147483648, -2147483648)
float %f = 1*(2**31)
  i32 %b = 0x0f800000 (260046848)
source: 0x0 (0)
target: 0x1 (1, -1)

$ ~/src/alive-nj/run.py /tmp/sgt.txt
----------                                                                      
Name: sgt
  %f   = uitofp i32 %i to float
  %b   = bitcast float %f to i32
  %cmp = icmp sgt i32 %b, -1
=>
  %cmp = icmp sgt i32 %i, -1

ERROR: Mismatch in values for i1 %cmp                                           

Example:
  i32 %i = 0x80000000 (2147483648, -2147483648)
float %f = 1*(2**31)
  i32 %b = 0x0f800000 (260046848)
source: 0x1 (1, -1)
target: 0x0 (0)

```

Sorry, let me remove that pass..


Repository:
  rL LLVM

https://reviews.llvm.org/D44421