[PATCH] D29014: [SelDag] Add FREEZE

Tue Mar 24 06:57:19 PDT 2020

aqjune marked an inline comment as done.
aqjune added inline comments.

================
Comment at: llvm/test/CodeGen/X86/freeze-legalize.ll:8-12
+; CHECK-NEXT:    movl $303174162, %eax ## imm = 0x12121212
+; CHECK-NEXT:    movl $875836468, %ecx ## imm = 0x34343434
+; CHECK-NEXT:    movl $1448498774, %edx ## imm = 0x56565656
+; CHECK-NEXT:    xorl %eax, %edx
+; CHECK-NEXT:    movl $2021161080, %eax ## imm = 0x78787878
----------------
spatel wrote:
> aqjune wrote:
> > aqjune wrote:
> > > spatel wrote:
> > > > Do we need to add basic simplify / constant folding for SDAG ?
> > > > freeze ( Constant ) --> Constant
> > > Yes, I agree it will be great. Do you want to make this patch contain the change as well?
> > Or I can land this first, and add the simplify / constant folding for SDAG.
> > I prefer incrementally making things because this patch itself is a big change.
> I prefer smaller patches too. Let's make that a follow-up. 
> 
> Is it correct that there is very little chance that this patch will create a visible performance regression (because there should be almost no freeze instruction creation in IR yet)?
Yes, it is.
Currently there is only one place where freeze is introduced - https://reviews.llvm.org/D76179
I checked that from assembly outputs of LLVM test-suite , only 3 / 5239 files are affected by this patch.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D29014/new/

https://reviews.llvm.org/D29014