https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69231
Bug ID: 69231 Summary: rtx_cost of subreg is bad for <= wordmode integral subregs of > wordmode integral pseudos Product: gcc Version: 6.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: jakub at gcc dot gnu.org CC: bernds at gcc dot gnu.org, hjl.tools at gmail dot com, jakub at gcc dot gnu.org, ktkachov at gcc dot gnu.org, law at gcc dot gnu.org, nheghathivhistha at gmail dot com, unassigned at gcc dot gnu.org Depends on: 67462 Target Milestone: --- +++ This bug was initially created as a clone of Bug #67462 +++ As mentioned in the PR67462, rtx_cost for SUBREG uses !MODES_TIEABLE_P and in that case uses fairly high cost. But, for say SImode subreg of DImode if the pseudo is likely to end up in a GPR on i?86, the actual cost is 0 (the same as of say SImode REG). So we should for GCC 7 consider changing this. Referenced Bugs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67462 [Bug 67462] [6 Regression] FAIL: gcc.dg/ifcvt-3.c scan-rtl-dump ce1 "3 true changes made"