Index: lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -4506,6 +4506,15 @@
         return New;
   }
 
+  // Zero-equality checks are preserved through unsigned floating-point casts:
+  // icmp eq (bitcast (uitofp X)), 0 --> icmp eq X, 0
+  // icmp ne (bitcast (uitofp X)), 0 --> icmp ne X, 0
+  Value *X;
+  if (match(Op0, m_BitCast(m_UIToFP(m_Value(X))))) {
+    if (I.isEquality() && match(Op1, m_Zero()))
+      return new ICmpInst(Pred, X, ConstantInt::getNullValue(X->getType()));
+  }
+
   // Test to see if the operands of the icmp are casted versions of other
   // values.  If the ptr->ptr cast can be stripped off both arguments, we do so
   // now.
Index: test/Transforms/InstCombine/cast-unsigned-icmp-eqcmp-0.ll
===================================================================
--- test/Transforms/InstCombine/cast-unsigned-icmp-eqcmp-0.ll
+++ test/Transforms/InstCombine/cast-unsigned-icmp-eqcmp-0.ll
@@ -8,11 +8,11 @@
 ; FIXME: *all* of these are true tests.
 ; In *all* of these, uitofp and bitcast should be instcombine'd out.
 
+; FIXME: icmp eq/ne does not ignore undef elements in vectors.
+
 define i1 @i32_cast_cmp_eq_int_0_uitofp_float(i32 %i) {
 ; CHECK-LABEL: @i32_cast_cmp_eq_int_0_uitofp_float(
-; CHECK-NEXT:    [[F:%.*]] = uitofp i32 [[I:%.*]] to float
-; CHECK-NEXT:    [[B:%.*]] = bitcast float [[F]] to i32
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[B]], 0
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[I:%.*]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %f = uitofp i32 %i to float
@@ -23,9 +23,7 @@
 
 define <2 x i1> @i32_cast_cmp_eq_int_0_uitofp_float_vec(<2 x i32> %i) {
 ; CHECK-LABEL: @i32_cast_cmp_eq_int_0_uitofp_float_vec(
-; CHECK-NEXT:    [[F:%.*]] = uitofp <2 x i32> [[I:%.*]] to <2 x float>
-; CHECK-NEXT:    [[B:%.*]] = bitcast <2 x float> [[F]] to <2 x i32>
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i32> [[B]], zeroinitializer
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i32> [[I:%.*]], zeroinitializer
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
   %f = uitofp <2 x i32> %i to  <2 x float>
@@ -49,9 +47,7 @@
 
 define i1 @i32_cast_cmp_ne_int_0_uitofp_float(i32 %i) {
 ; CHECK-LABEL: @i32_cast_cmp_ne_int_0_uitofp_float(
-; CHECK-NEXT:    [[F:%.*]] = uitofp i32 [[I:%.*]] to float
-; CHECK-NEXT:    [[B:%.*]] = bitcast float [[F]] to i32
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[B]], 0
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[I:%.*]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %f = uitofp i32 %i to float
@@ -62,9 +58,7 @@
 
 define <2 x i1> @i32_cast_cmp_ne_int_0_uitofp_float_vec(<2 x i32> %i) {
 ; CHECK-LABEL: @i32_cast_cmp_ne_int_0_uitofp_float_vec(
-; CHECK-NEXT:    [[F:%.*]] = uitofp <2 x i32> [[I:%.*]] to <2 x float>
-; CHECK-NEXT:    [[B:%.*]] = bitcast <2 x float> [[F]] to <2 x i32>
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ne <2 x i32> [[B]], zeroinitializer
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne <2 x i32> [[I:%.*]], zeroinitializer
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
   %f = uitofp <2 x i32> %i to  <2 x float>
@@ -88,9 +82,7 @@
 
 define i1 @i32_cast_cmp_eq_int_0_uitofp_double(i32 %i) {
 ; CHECK-LABEL: @i32_cast_cmp_eq_int_0_uitofp_double(
-; CHECK-NEXT:    [[F:%.*]] = uitofp i32 [[I:%.*]] to double
-; CHECK-NEXT:    [[B:%.*]] = bitcast double [[F]] to i64
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i64 [[B]], 0
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[I:%.*]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %f = uitofp i32 %i to double
@@ -101,9 +93,7 @@
 
 define <2 x i1> @i32_cast_cmp_eq_int_0_uitofp_double_vec(<2 x i32> %i) {
 ; CHECK-LABEL: @i32_cast_cmp_eq_int_0_uitofp_double_vec(
-; CHECK-NEXT:    [[F:%.*]] = uitofp <2 x i32> [[I:%.*]] to <2 x double>
-; CHECK-NEXT:    [[B:%.*]] = bitcast <2 x double> [[F]] to <2 x i64>
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i64> [[B]], zeroinitializer
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i32> [[I:%.*]], zeroinitializer
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
   %f = uitofp <2 x i32> %i to  <2 x double>
@@ -127,9 +117,7 @@
 
 define i1 @i32_cast_cmp_ne_int_0_uitofp_double(i32 %i) {
 ; CHECK-LABEL: @i32_cast_cmp_ne_int_0_uitofp_double(
-; CHECK-NEXT:    [[F:%.*]] = uitofp i32 [[I:%.*]] to double
-; CHECK-NEXT:    [[B:%.*]] = bitcast double [[F]] to i64
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i64 [[B]], 0
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[I:%.*]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %f = uitofp i32 %i to double
@@ -140,9 +128,7 @@
 
 define <2 x i1> @i32_cast_cmp_ne_int_0_uitofp_double_vec(<2 x i32> %i) {
 ; CHECK-LABEL: @i32_cast_cmp_ne_int_0_uitofp_double_vec(
-; CHECK-NEXT:    [[F:%.*]] = uitofp <2 x i32> [[I:%.*]] to <2 x double>
-; CHECK-NEXT:    [[B:%.*]] = bitcast <2 x double> [[F]] to <2 x i64>
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ne <2 x i64> [[B]], zeroinitializer
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne <2 x i32> [[I:%.*]], zeroinitializer
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
   %f = uitofp <2 x i32> %i to  <2 x double>
@@ -166,9 +152,7 @@
 
 define i1 @i32_cast_cmp_eq_int_0_uitofp_half(i32 %i) {
 ; CHECK-LABEL: @i32_cast_cmp_eq_int_0_uitofp_half(
-; CHECK-NEXT:    [[F:%.*]] = uitofp i32 [[I:%.*]] to half
-; CHECK-NEXT:    [[B:%.*]] = bitcast half [[F]] to i16
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i16 [[B]], 0
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[I:%.*]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %f = uitofp i32 %i to half
@@ -179,9 +163,7 @@
 
 define <2 x i1> @i32_cast_cmp_eq_int_0_uitofp_half_vec(<2 x i32> %i) {
 ; CHECK-LABEL: @i32_cast_cmp_eq_int_0_uitofp_half_vec(
-; CHECK-NEXT:    [[F:%.*]] = uitofp <2 x i32> [[I:%.*]] to <2 x half>
-; CHECK-NEXT:    [[B:%.*]] = bitcast <2 x half> [[F]] to <2 x i16>
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i16> [[B]], zeroinitializer
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i32> [[I:%.*]], zeroinitializer
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
   %f = uitofp <2 x i32> %i to  <2 x half>
@@ -205,9 +187,7 @@
 
 define i1 @i32_cast_cmp_ne_int_0_uitofp_half(i32 %i) {
 ; CHECK-LABEL: @i32_cast_cmp_ne_int_0_uitofp_half(
-; CHECK-NEXT:    [[F:%.*]] = uitofp i32 [[I:%.*]] to half
-; CHECK-NEXT:    [[B:%.*]] = bitcast half [[F]] to i16
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i16 [[B]], 0
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[I:%.*]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %f = uitofp i32 %i to half
@@ -218,9 +198,7 @@
 
 define <2 x i1> @i32_cast_cmp_ne_int_0_uitofp_half_vec(<2 x i32> %i) {
 ; CHECK-LABEL: @i32_cast_cmp_ne_int_0_uitofp_half_vec(
-; CHECK-NEXT:    [[F:%.*]] = uitofp <2 x i32> [[I:%.*]] to <2 x half>
-; CHECK-NEXT:    [[B:%.*]] = bitcast <2 x half> [[F]] to <2 x i16>
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ne <2 x i16> [[B]], zeroinitializer
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne <2 x i32> [[I:%.*]], zeroinitializer
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
   %f = uitofp <2 x i32> %i to  <2 x half>