[X86] Allow folding of stack reloads when loading a subreg of the spilled reg
We did not support subregs in InlineSpiller:foldMemoryOperand() because targets
may not deal with them correctly.
This adds a target hook to let the spiller know that a target can handle
subregs, and actually enables it for x86 for the case of stack slot reloads.
This fixes PR30832.
Differential Revision: https://reviews.llvm.org/D26521
llvm-svn: 287792
diff --git a/llvm/test/CodeGen/X86/partial-fold64.ll b/llvm/test/CodeGen/X86/partial-fold64.ll
index b9ea7d6..15c9d19 100644
--- a/llvm/test/CodeGen/X86/partial-fold64.ll
+++ b/llvm/test/CodeGen/X86/partial-fold64.ll
@@ -3,8 +3,7 @@
define i32 @fold64to32(i64 %add, i32 %spill) {
; CHECK-LABEL: fold64to32:
; CHECK: movq %rdi, -{{[0-9]+}}(%rsp) # 8-byte Spill
-; CHECK: movq -{{[0-9]+}}(%rsp), %rax # 8-byte Reload
-; CHECK: subl %eax, %esi
+; CHECK: subl -{{[0-9]+}}(%rsp), %esi # 4-byte Folded Reload
entry:
tail call void asm sideeffect "", "~{rax},~{rbx},~{rcx},~{rdx},~{rdi},~{rbp},~{r8},~{r9},~{r10},~{r11},~{r12},~{r13},~{r14},~{r15},~{dirflag},~{fpsr},~{flags}"()
%trunc = trunc i64 %add to i32
@@ -15,8 +14,7 @@
define i8 @fold64to8(i64 %add, i8 %spill) {
; CHECK-LABEL: fold64to8:
; CHECK: movq %rdi, -{{[0-9]+}}(%rsp) # 8-byte Spill
-; CHECK: movq -{{[0-9]+}}(%rsp), %rax # 8-byte Reload
-; CHECK: subb %al, %sil
+; CHECK: subb -{{[0-9]+}}(%rsp), %sil # 1-byte Folded Reload
entry:
tail call void asm sideeffect "", "~{rax},~{rbx},~{rcx},~{rdx},~{rdi},~{rbp},~{r8},~{r9},~{r10},~{r11},~{r12},~{r13},~{r14},~{r15},~{dirflag},~{fpsr},~{flags}"()
%trunc = trunc i64 %add to i8