1 files changed, 33 insertions, 13 deletions
diff --git a/llvm/lib/CodeGen/GlobalISel/GISelValueTracking.cpp b/llvm/lib/CodeGen/GlobalISel/GISelValueTracking.cpp
index 692befde71cb..6650ad25bed0 100644
--- a/llvm/lib/CodeGen/GlobalISel/GISelValueTracking.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/GISelValueTracking.cpp
@@ -222,12 +222,11 @@ void GISelValueTracking::computeKnownBitsImpl(Register R, KnownBits &Known,
     // Collect the known bits that are shared by every demanded vector element.
     Known.Zero.setAllBits();
     Known.One.setAllBits();
-    for (unsigned i = 0, e = MI.getNumOperands() - 1; i < e; ++i) {
-      if (!DemandedElts[i])
+    for (const auto &[I, MO] : enumerate(drop_begin(MI.operands()))) {
+      if (!DemandedElts[I])
         continue;
 
-      computeKnownBitsImpl(MI.getOperand(i + 1).getReg(), Known2, APInt(1, 1),
-                           Depth + 1);
+      computeKnownBitsImpl(MO.getReg(), Known2, APInt(1, 1), Depth + 1);
 
       // Known bits are the values that are shared by every demanded element.
       Known = Known.intersectWith(Known2);
@@ -683,14 +682,12 @@ void GISelValueTracking::computeKnownBitsImpl(Register R, KnownBits &Known,
     Known.One.setAllBits();
     unsigned NumSubVectorElts =
         MRI.getType(MI.getOperand(1).getReg()).getNumElements();
-    unsigned NumSubVectors = MI.getNumOperands() - 1;
 
-    for (unsigned i = 0; i != NumSubVectors; ++i) {
+    for (const auto &[I, MO] : enumerate(drop_begin(MI.operands()))) {
       APInt DemandedSub =
-          DemandedElts.extractBits(NumSubVectorElts, i * NumSubVectorElts);
+          DemandedElts.extractBits(NumSubVectorElts, I * NumSubVectorElts);
       if (!!DemandedSub) {
-        computeKnownBitsImpl(MI.getOperand(i + 1).getReg(), Known2, DemandedSub,
-                             Depth + 1);
+        computeKnownBitsImpl(MO.getReg(), Known2, DemandedSub, Depth + 1);
 
         Known = Known.intersectWith(Known2);
       }
@@ -1944,12 +1941,35 @@ unsigned GISelValueTracking::computeNumSignBits(Register R,
     // Collect the known bits that are shared by every demanded vector element.
     FirstAnswer = TyBits;
     APInt SingleDemandedElt(1, 1);
-    for (unsigned i = 0, e = MI.getNumOperands() - 1; i < e; ++i) {
-      if (!DemandedElts[i])
+    for (const auto &[I, MO] : enumerate(drop_begin(MI.operands()))) {
+      if (!DemandedElts[I])
+        continue;
+
+      unsigned Tmp2 =
+          computeNumSignBits(MO.getReg(), SingleDemandedElt, Depth + 1);
+      FirstAnswer = std::min(FirstAnswer, Tmp2);
+
+      // If we don't know any bits, early out.
+      if (FirstAnswer == 1)
+        break;
+    }
+    break;
+  }
+  case TargetOpcode::G_CONCAT_VECTORS: {
+    if (MRI.getType(MI.getOperand(0).getReg()).isScalableVector())
+      break;
+    FirstAnswer = TyBits;
+    // Determine the minimum number of sign bits across all demanded
+    // elts of the input vectors. Early out if the result is already 1.
+    unsigned NumSubVectorElts =
+        MRI.getType(MI.getOperand(1).getReg()).getNumElements();
+    for (const auto &[I, MO] : enumerate(drop_begin(MI.operands()))) {
+      APInt DemandedSub =
+          DemandedElts.extractBits(NumSubVectorElts, I * NumSubVectorElts);
+      if (!DemandedSub)
         continue;
+      unsigned Tmp2 = computeNumSignBits(MO.getReg(), DemandedSub, Depth + 1);
 
-      unsigned Tmp2 = computeNumSignBits(MI.getOperand(i + 1).getReg(),
-                                         SingleDemandedElt, Depth + 1);
       FirstAnswer = std::min(FirstAnswer, Tmp2);
 
       // If we don't know any bits, early out.