[llvm] [SDAG] Fix deferring constrained function calls (PR #153029)

[Serge Pavlov via llvm-commits]

================
@@ -100,43 +100,6 @@ entry:
   ret i32 %result
 }
 
-; These 2 divs only differ in their exception behavior and will be CSEd. Make
-; sure the nofpexcept flag is not set on the combined node.
-define void @binop_cse(double %a, double %b, ptr %x, ptr %y) #0 {
-entry:
-; CHECK-LABEL: name: binop_cse
-; CHECK: [[MOV32rm:%[0-9]+]]:gr32 = MOV32rm %fixed-stack.0, 1, $noreg, 0, $noreg :: (load (s32) from %fixed-stack.0)
-; CHECK: [[MOV32rm1:%[0-9]+]]:gr32 = MOV32rm %fixed-stack.1, 1, $noreg, 0, $noreg :: (load (s32) from %fixed-stack.1, align 16)
-; CHECK: [[MOVSDrm_alt:%[0-9]+]]:fr64 = MOVSDrm_alt %fixed-stack.3, 1, $noreg, 0, $noreg :: (load (s64) from %fixed-stack.3, align 16)
-; CHECK: %3:fr64 = DIVSDrm [[MOVSDrm_alt]], %fixed-stack.2, 1, $noreg, 0, $noreg, implicit $mxcsr :: (load (s64) from %fixed-stack.2)
-; CHECK: MOVSDmr killed [[MOV32rm1]], 1, $noreg, 0, $noreg, %3 :: (store (s64) into %ir.x, align 4)
-; CHECK: MOVSDmr killed [[MOV32rm]], 1, $noreg, 0, $noreg, %3 :: (store (s64) into %ir.y, align 4)
-; CHECK: RET 0
-  %div = call double @llvm.experimental.constrained.fdiv.f64(double %a, double %b, metadata !"round.dynamic", metadata !"fpexcept.strict") #0
-  %div2 = call double @llvm.experimental.constrained.fdiv.f64(double %a, double %b, metadata !"round.dynamic", metadata !"fpexcept.ignore") #0
-  store double %div, ptr %x
-  store double %div2, ptr %y
-  ret void
-}
-
-; These 2 sitofps only differ in their exception behavior and will be CSEd. Make
-; sure the nofpexcept flag is not set on the combined node.
-define void @sitofp_cse(i32 %a, ptr %x, ptr %y) #0 {
-entry:
-; CHECK-LABEL: name: sitofp_cse
-; CHECK: [[MOV32rm:%[0-9]+]]:gr32 = MOV32rm %fixed-stack.0, 1, $noreg, 0, $noreg :: (load (s32) from %fixed-stack.0, align 8)
-; CHECK: [[MOV32rm1:%[0-9]+]]:gr32 = MOV32rm %fixed-stack.1, 1, $noreg, 0, $noreg :: (load (s32) from %fixed-stack.1)
-; CHECK: %2:fr64 = CVTSI2SDrm %fixed-stack.2, 1, $noreg, 0, $noreg :: (load (s32) from %fixed-stack.2, align 16)
-; CHECK: MOVSDmr killed [[MOV32rm1]], 1, $noreg, 0, $noreg, %2 :: (store (s64) into %ir.x, align 4)
-; CHECK: MOVSDmr killed [[MOV32rm]], 1, $noreg, 0, $noreg, %2 :: (store (s64) into %ir.y, align 4)
-; CHECK: RET 0
-  %result = call double @llvm.experimental.constrained.sitofp.f64.i32(i32 %a, metadata !"round.dynamic", metadata !"fpexcept.strict") #0
-  %result2 = call double @llvm.experimental.constrained.sitofp.f64.i32(i32 %a, metadata !"round.dynamic", metadata !"fpexcept.ignore") #0
-  store double %result, ptr %x
-  store double %result2, ptr %y
-  ret void
-}
-
----------------
spavloff wrote:

I put back the tests and slightly modified them to check changes introduced by this patch. Previously the two operation in the test were merged because the nodes were identical, due to the same value of chain argument. If the instructions are sequenced, which this patch implements, the chain arguments become different and the nodes are not merged.

It is not an error that the nodes were merged previously, but it was made using CSE mechanism. With sequenced node it does not work. Merging such nodes require another mechanism, probably at IR level.

https://github.com/llvm/llvm-project/pull/153029