Index: llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -7268,9 +7268,16 @@
   // Vector selects can have a scalar predicate. If so, splat into a vector and
   // finish for later legalization attempts to try again.
   if (MaskTy.isScalar()) {
+    // FIXME: We shouldn't be promoting the mask type here, or even the
+    // broadcast. The broadcast should probably be handled as MoreElements, not
+    // lower.
     Register MaskElt = MaskReg;
-    if (MaskTy.getSizeInBits() < DstTy.getScalarSizeInBits())
-      MaskElt = MIRBuilder.buildSExt(DstTy.getElementType(), MaskElt).getReg(0);
+    if (MaskTy.getSizeInBits() < DstTy.getScalarSizeInBits()) {
+      // FIXME: We have no way of knowing if this is FP without the original
+      // boolean's context.
+      MaskElt = MIRBuilder.buildBoolExt(DstTy.getElementType(),
+                                        MaskElt, false).getReg(0);
+    }
     // Generate a vector splat idiom to be pattern matched later.
     auto ShufSplat = MIRBuilder.buildShuffleSplat(DstTy, MaskElt);
     Observer.changingInstr(MI);