[DAGCombiner] Do not generate ISD::ADDE node if adde is not legal for the target when combine ISD::TRUNC node

Do not combine (trunc adde(X, Y, Carry)) into (adde trunc(X), trunc(Y), Carry), 
if adde is not legal for the target. Even it's at type-legalize phase. 
Because adde is special and will not be legalized at operation-legalize phase later.

This fixes: PR40922
https://bugs.llvm.org/show_bug.cgi?id=40922

Differential Revision: https://reviews.llvm.org//D60854

llvm-svn: 359532

3 files changed, 41 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index df1929bf36b..aeab54d65a8 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -10257,7 +10257,9 @@ SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
   // When the adde's carry is not used.
   if ((N0.getOpcode() == ISD::ADDE || N0.getOpcode() == ISD::ADDCARRY) &&
       N0.hasOneUse() && !N0.getNode()->hasAnyUseOfValue(1) &&
-      (!LegalOperations || TLI.isOperationLegal(N0.getOpcode(), VT))) {
+      // We only do for addcarry before legalize operation
+      ((!LegalOperations && N0.getOpcode() == ISD::ADDCARRY) ||
+       TLI.isOperationLegal(N0.getOpcode(), VT))) {
     SDLoc SL(N);
     auto X = DAG.getNode(ISD::TRUNCATE, SL, VT, N0.getOperand(0));
     auto Y = DAG.getNode(ISD::TRUNCATE, SL, VT, N0.getOperand(1));
diff --git a/llvm/test/CodeGen/PowerPC/pr39815.ll b/llvm/test/CodeGen/PowerPC/pr39815.ll
index a01c8be8634..062e055167c 100644
--- a/llvm/test/CodeGen/PowerPC/pr39815.ll
+++ b/llvm/test/CodeGen/PowerPC/pr39815.ll
@@ -20,10 +20,9 @@ entry:
 ; CHECK:      # %bb.0:
 ; CHECK-DAG:   addis [[REG1:[0-9]+]], [[REG2:[0-9]+]], [[VAR1:[a-z0-9A-Z_.]+]]@toc@ha
 ; CHECK-DAG:   ld [[REG3:[0-9]+]], [[VAR1]]@toc@l([[REG1]])
-; CHECK-DAG:   lbz [[REG4:[0-9]+]], 0([[REG3]])
+; CHECK-DAG:   lwz [[REG4:[0-9]+]], 0([[REG3]])
 ; CHECK-DAG:   addic [[REG5:[0-9]+]], [[REG3]], -1
-; CHECK-DAG:   extsb [[REG6:[0-9]+]], [[REG4]]
-; CHECK-DAG:   addze [[REG7:[0-9]+]], [[REG6]]
+; CHECK-DAG:   addze [[REG7:[0-9]+]], [[REG4]]
 ; CHECK-DAG:   addis [[REG8:[0-9]+]], [[REG2]], [[VAR2:[a-z0-9A-Z_.]+]]@toc@ha
 ; CHECK-DAG:   andi. [[REG9:[0-9]+]], [[REG7]], 5
 ; CHECK-DAG:   stb [[REG9]], [[VAR2]]@toc@l([[REG8]])
diff --git a/llvm/test/CodeGen/PowerPC/pr40922.ll b/llvm/test/CodeGen/PowerPC/pr40922.ll
new file mode 100644
index 00000000000..291070bdd24
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/pr40922.ll
@@ -0,0 +1,36 @@
+; RUN: llc -verify-machineinstrs -mtriple=powerpc-unknown-linux-gnu < %s | FileCheck %s
+
+; Test case adapted from PR40922.
+
+@a.b = internal global i32 0, align 4
+
+define i32 @a() {
+entry:
+  %call = tail call i32 bitcast (i32 (...)* @d to i32 ()*)()
+  %0 = load i32, i32* @a.b, align 4
+  %conv = zext i32 %0 to i64
+  %add = add nuw nsw i64 %conv, 6
+  %and = and i64 %add, 8589934575
+  %cmp = icmp ult i64 %and, %conv
+  br i1 %cmp, label %if.then, label %if.end
+
+if.then:                                          ; preds = %entry
+  %call3 = tail call i32 bitcast (i32 (...)* @e to i32 ()*)()
+  br label %if.end
+
+if.end:                                           ; preds = %if.then, %entry
+  store i32 %call, i32* @a.b, align 4
+  ret i32 undef
+}
+
+; CHECK-LABEL: @a
+; CHECK: li 5, 0
+; CHECK: mr 30, 3
+; CHECK: addic 6, 4, 6
+; CHECK: addze 5, 5
+; CHECK: rlwinm 6, 6, 0, 28, 26
+; CHECK: andi. 5, 5, 1
+
+declare i32 @d(...)
+
+declare i32 @e(...)