[PATCH] D44909: [DAGCombine] (float)((int) f) --> ftrunc (PR36617)

[Nemanja Ivanovic via Phabricator via llvm-commits]

nemanjai accepted this revision.
nemanjai added a comment.
This revision is now accepted and ready to land.

Ah, OK. The language reference clearly states that unrepresentable values produce undefined results. As far as PPC is concerned, this LGTM.

P.S. If you think it's appropriate, perhaps it would be nice to add this PPC test case since PPC has `FTRUNC` for vectors as well:

  ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
  ; RUN: llc -mcpu=pwr8 -mtriple=powerpc64le-unknown-unknown \
  ; RUN:   -verify-machineinstrs < %s | FileCheck %s
  
  define <4 x float> @truncf32(<4 x float> %a) {
  ; CHECK-LABEL: truncf32:
  ; CHECK:       # %bb.0: # %entry
  ; CHECK-NEXT:    xvrspiz 34, 34
  ; CHECK-NEXT:    blr
  entry:
    %0 = fptosi <4 x float> %a to <4 x i32>
    %1 = sitofp <4 x i32> %0 to <4 x float>
    ret <4 x float> %1
  }
  
  define <2 x double> @truncf64(<2 x double> %a) {
  ; CHECK-LABEL: truncf64:
  ; CHECK:       # %bb.0: # %entry
  ; CHECK-NEXT:    xvrdpiz 34, 34
  ; CHECK-NEXT:    blr
  entry:
    %0 = fptosi <2 x double> %a to <2 x i64>
    %1 = sitofp <2 x i64> %0 to <2 x double>
    ret <2 x double> %1
  }
  
  define <4 x float> @truncf32u(<4 x float> %a) {
  ; CHECK-LABEL: truncf32u:
  ; CHECK:       # %bb.0: # %entry
  ; CHECK-NEXT:    xvrspiz 34, 34
  ; CHECK-NEXT:    blr
  entry:
    %0 = fptoui <4 x float> %a to <4 x i32>
    %1 = uitofp <4 x i32> %0 to <4 x float>
    ret <4 x float> %1
  }
  
  define <2 x double> @truncf64u(<2 x double> %a) {
  ; CHECK-LABEL: truncf64u:
  ; CHECK:       # %bb.0: # %entry
  ; CHECK-NEXT:    xvrdpiz 34, 34
  ; CHECK-NEXT:    blr
  entry:
    %0 = fptoui <2 x double> %a to <2 x i64>
    %1 = uitofp <2 x i64> %0 to <2 x double>
    ret <2 x double> %1
  }


https://reviews.llvm.org/D44909