[PATCH] D107174: [DAG] isGuaranteedNotToBeUndefOrPoison - handle ISD::BUILD_VECTOR nodes

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: efriedma, spatel, lebedev.ri, aqjune.
Herald added subscribers: pengfei, hiraditya.
RKSimon requested review of this revision.
Herald added a project: LLVM.

If all demanded elements of the BUILD_VECTOR pass a isGuaranteedNotToBeUndefOrPoison check, then we can treat this specific demanded use of the BUILD_VECTOR as guaranteed not to be undef or poison either.

NOTE: BUILD_VECTOR has implicit truncation of wider scalar elements - this shouldn't affect the result afaict.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D107174

Files:
  llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
  llvm/test/CodeGen/X86/freeze-constant-fold.ll
  llvm/test/CodeGen/X86/freeze-legalize.ll


Index: llvm/test/CodeGen/X86/freeze-legalize.ll
===================================================================
--- llvm/test/CodeGen/X86/freeze-legalize.ll
+++ llvm/test/CodeGen/X86/freeze-legalize.ll
@@ -46,7 +46,7 @@
 define <2 x i10> @promote_vec() {
 ; CHECK-LABEL: promote_vec:
 ; CHECK:       ## %bb.0:
-; CHECK-NEXT:    movw $1674, %ax ## imm = 0x68A
+; CHECK-NEXT:    movw $650, %ax ## imm = 0x28A
 ; CHECK-NEXT:    movw $518, %dx ## imm = 0x206
 ; CHECK-NEXT:    retl
   %a = freeze <2 x i10> <i10 682, i10 125>
Index: llvm/test/CodeGen/X86/freeze-constant-fold.ll
===================================================================
--- llvm/test/CodeGen/X86/freeze-constant-fold.ll
+++ llvm/test/CodeGen/X86/freeze-constant-fold.ll
@@ -15,7 +15,6 @@
   ret i32 %5
 }
 
-; FIXME: X86 scalarization sees through the freeze, but vector types don't.
 define <4 x i32> @fold_add_freeze_v4i32() {
 ; X86-LABEL: fold_add_freeze_v4i32:
 ; X86:       # %bb.0:
@@ -28,9 +27,7 @@
 ;
 ; X64-LABEL: fold_add_freeze_v4i32:
 ; X64:       # %bb.0:
-; X64-NEXT:    pxor %xmm1, %xmm1
 ; X64-NEXT:    pcmpeqd %xmm0, %xmm0
-; X64-NEXT:    paddd %xmm1, %xmm0
 ; X64-NEXT:    retq
   %1 = insertelement <4 x i32> poison, i32 0, i32 0
   %2 = shufflevector <4 x i32> %1, <4 x i32> poison, <4 x i32> zeroinitializer
Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -4285,7 +4285,15 @@
   case ISD::UNDEF:
     return PoisonOnly;
 
-  // TODO: ISD::BUILD_VECTOR handling
+  case ISD::BUILD_VECTOR:
+    for (unsigned i = 0, e = Op.getNumOperands(); i < e; ++i) {
+      if (!DemandedElts[i])
+        continue;
+      if (!isGuaranteedNotToBeUndefOrPoison(Op.getOperand(i), PoisonOnly,
+                                            Depth + 1))
+        return false;
+    }
+    return true;
 
   // TODO: Search for noundef attributes from library functions.
 


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