diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -5459,12 +5459,12 @@
     if (N0 != N2 && (N2.getOpcode() != ISD::TRUNCATE || N0 != N2.getOperand(0)))
       return 0;
     // The constants need to be the same or a truncated version of each other.
-    ConstantSDNode *N1C = isConstOrConstSplat(N1);
-    ConstantSDNode *N3C = isConstOrConstSplat(N3);
+    ConstantSDNode *N1C = isConstOrConstSplat(peekThroughTruncates(N1));
+    ConstantSDNode *N3C = isConstOrConstSplat(peekThroughTruncates(N3));
     if (!N1C || !N3C)
       return 0;
-    const APInt &C1 = N1C->getAPIntValue();
-    const APInt &C2 = N3C->getAPIntValue();
+    const APInt &C1 = N1C->getAPIntValue().trunc(N1.getScalarValueSizeInBits());
+    const APInt &C2 = N3C->getAPIntValue().trunc(N3.getScalarValueSizeInBits());
     if (C1.getBitWidth() < C2.getBitWidth() || C1 != C2.sext(C1.getBitWidth()))
       return 0;
     return CC == ISD::SETLT ? ISD::SMIN : (CC == ISD::SETGT ? ISD::SMAX : 0);
diff --git a/llvm/test/CodeGen/X86/fpclamptosat.ll b/llvm/test/CodeGen/X86/fpclamptosat.ll
--- a/llvm/test/CodeGen/X86/fpclamptosat.ll
+++ b/llvm/test/CodeGen/X86/fpclamptosat.ll
@@ -407,25 +407,16 @@
 
 ; i64 saturate
 
-; FIXME: Failure to recognise the i128 is in i64 bounds.
 define i64 @stest_f64i64(double %x) nounwind {
 ; CHECK-LABEL: stest_f64i64:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    pushq %rax
-; CHECK-NEXT:    callq __fixdfti@PLT
-; CHECK-NEXT:    xorl %ecx, %ecx
-; CHECK-NEXT:    movabsq $9223372036854775807, %rsi # imm = 0x7FFFFFFFFFFFFFFF
-; CHECK-NEXT:    cmpq %rsi, %rax
-; CHECK-NEXT:    movq %rdx, %rdi
-; CHECK-NEXT:    sbbq $0, %rdi
-; CHECK-NEXT:    cmovlq %rdx, %rcx
-; CHECK-NEXT:    cmovgeq %rsi, %rax
-; CHECK-NEXT:    movabsq $-9223372036854775808, %rdx # imm = 0x8000000000000000
-; CHECK-NEXT:    cmpq %rax, %rdx
-; CHECK-NEXT:    movq $-1, %rsi
-; CHECK-NEXT:    sbbq %rcx, %rsi
-; CHECK-NEXT:    cmovgeq %rdx, %rax
-; CHECK-NEXT:    popq %rcx
+; CHECK-NEXT:    cvttsd2si %xmm0, %rax
+; CHECK-NEXT:    ucomisd {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
+; CHECK-NEXT:    movabsq $9223372036854775807, %rcx # imm = 0x7FFFFFFFFFFFFFFF
+; CHECK-NEXT:    cmovbeq %rax, %rcx
+; CHECK-NEXT:    xorl %eax, %eax
+; CHECK-NEXT:    ucomisd %xmm0, %xmm0
+; CHECK-NEXT:    cmovnpq %rcx, %rax
 ; CHECK-NEXT:    retq
 entry:
   %conv = fptosi double %x to i128
@@ -482,25 +473,16 @@
   ret i64 %conv6
 }
 
-; FIXME: Failure to recognise the i128 is in i64 bounds.
 define i64 @stest_f32i64(float %x) nounwind {
 ; CHECK-LABEL: stest_f32i64:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    pushq %rax
-; CHECK-NEXT:    callq __fixsfti@PLT
-; CHECK-NEXT:    xorl %ecx, %ecx
-; CHECK-NEXT:    movabsq $9223372036854775807, %rsi # imm = 0x7FFFFFFFFFFFFFFF
-; CHECK-NEXT:    cmpq %rsi, %rax
-; CHECK-NEXT:    movq %rdx, %rdi
-; CHECK-NEXT:    sbbq $0, %rdi
-; CHECK-NEXT:    cmovlq %rdx, %rcx
-; CHECK-NEXT:    cmovgeq %rsi, %rax
-; CHECK-NEXT:    movabsq $-9223372036854775808, %rdx # imm = 0x8000000000000000
-; CHECK-NEXT:    cmpq %rax, %rdx
-; CHECK-NEXT:    movq $-1, %rsi
-; CHECK-NEXT:    sbbq %rcx, %rsi
-; CHECK-NEXT:    cmovgeq %rdx, %rax
-; CHECK-NEXT:    popq %rcx
+; CHECK-NEXT:    cvttss2si %xmm0, %rax
+; CHECK-NEXT:    ucomiss {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
+; CHECK-NEXT:    movabsq $9223372036854775807, %rcx # imm = 0x7FFFFFFFFFFFFFFF
+; CHECK-NEXT:    cmovbeq %rax, %rcx
+; CHECK-NEXT:    xorl %eax, %eax
+; CHECK-NEXT:    ucomiss %xmm0, %xmm0
+; CHECK-NEXT:    cmovnpq %rcx, %rax
 ; CHECK-NEXT:    retq
 entry:
   %conv = fptosi float %x to i128
@@ -557,24 +539,21 @@
   ret i64 %conv6
 }
 
-; FIXME: Failure to recognise the i128 is in i64 bounds.
 define i64 @stest_f16i64(half %x) nounwind {
 ; CHECK-LABEL: stest_f16i64:
 ; CHECK:       # %bb.0: # %entry
 ; CHECK-NEXT:    pushq %rax
-; CHECK-NEXT:    callq __fixhfti@PLT
-; CHECK-NEXT:    xorl %ecx, %ecx
-; CHECK-NEXT:    movabsq $9223372036854775807, %rsi # imm = 0x7FFFFFFFFFFFFFFF
-; CHECK-NEXT:    cmpq %rsi, %rax
-; CHECK-NEXT:    movq %rdx, %rdi
-; CHECK-NEXT:    sbbq $0, %rdi
-; CHECK-NEXT:    cmovlq %rdx, %rcx
-; CHECK-NEXT:    cmovgeq %rsi, %rax
-; CHECK-NEXT:    movabsq $-9223372036854775808, %rdx # imm = 0x8000000000000000
-; CHECK-NEXT:    cmpq %rax, %rdx
-; CHECK-NEXT:    movq $-1, %rsi
-; CHECK-NEXT:    sbbq %rcx, %rsi
-; CHECK-NEXT:    cmovgeq %rdx, %rax
+; CHECK-NEXT:    callq __extendhfsf2@PLT
+; CHECK-NEXT:    cvttss2si %xmm0, %rax
+; CHECK-NEXT:    ucomiss {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
+; CHECK-NEXT:    movabsq $-9223372036854775808, %rcx # imm = 0x8000000000000000
+; CHECK-NEXT:    cmovaeq %rax, %rcx
+; CHECK-NEXT:    ucomiss {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
+; CHECK-NEXT:    movabsq $9223372036854775807, %rdx # imm = 0x7FFFFFFFFFFFFFFF
+; CHECK-NEXT:    cmovbeq %rcx, %rdx
+; CHECK-NEXT:    xorl %eax, %eax
+; CHECK-NEXT:    ucomiss %xmm0, %xmm0
+; CHECK-NEXT:    cmovnpq %rdx, %rax
 ; CHECK-NEXT:    popq %rcx
 ; CHECK-NEXT:    retq
 entry: