Index: lib/Target/AArch64/AArch64ISelLowering.cpp
===================================================================
--- lib/Target/AArch64/AArch64ISelLowering.cpp
+++ lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -1822,6 +1822,37 @@
       }
     }
   }
+
+  // Swap operands if one side is foldable.
+  auto FoldableCmpOperand = [&] (SDNode *N) {
+    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(N))
+      return isLegalArithImmed(C->getZExtValue());
+    if (!N->hasOneUse())
+      return false;
+    if (N->getOpcode() == ISD::SHL ||
+        N->getOpcode() == ISD::SRL ||
+        N->getOpcode() == ISD::SRA)
+      return isa<ConstantSDNode>(N->getOperand(1));
+    if (N->getOpcode() == ISD::SIGN_EXTEND_INREG)
+      return true;
+    if (N->getOpcode() == ISD::AND) {
+      // In the future, this should probably be enhanced to handle
+      // cases where the operand of the AND is an LSL (e.g.
+      // "(x << 1) & 510" is "uxtb #1"). But isel can't
+      // handle it anyway at the moment.
+      SDNode *AndRHS = N->getOperand(1).getNode();
+      if (ConstantSDNode *RHSC = dyn_cast<ConstantSDNode>(AndRHS))
+        return RHSC->getAPIntValue() == 0xFF ||
+               RHSC->getAPIntValue() == 0xFFFF ||
+               RHSC->getAPIntValue() == 0xFFFFFFFF;
+    }
+    return false;
+  };
+  if (FoldableCmpOperand(LHS.getNode()) && !FoldableCmpOperand(RHS.getNode())) {
+    std::swap(LHS, RHS);
+    CC = ISD::getSetCCSwappedOperands(CC);
+  }
+
   SDValue Cmp;
   AArch64CC::CondCode AArch64CC;
   if ((CC == ISD::SETEQ || CC == ISD::SETNE) && isa<ConstantSDNode>(RHS)) {
Index: test/CodeGen/AArch64/cmp-commute.ll
===================================================================
--- /dev/null
+++ test/CodeGen/AArch64/cmp-commute.ll
@@ -0,0 +1,209 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=aarch64-unknown-linux-gnu < %s | FileCheck %s
+
+define i1 @shl_eq(i32 %x, i32 %y) nounwind {
+; CHECK-LABEL: shl_eq:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    cmp w0, w1, lsl #2
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %yy = shl i32 %y, 2
+  %cmp = icmp eq i32 %x, %yy
+  ret i1 %cmp
+}
+
+define i1 @shl_eq_2(i32 %x, i32 %y) nounwind {
+; CHECK-LABEL: shl_eq_2:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    cmp w0, w1, lsl #2
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %yy = shl i32 %y, 2
+  %cmp = icmp eq i32 %yy, %x
+  ret i1 %cmp
+}
+
+define i1 @shl_eq_small_const(i32 %y) nounwind {
+; CHECK-LABEL: shl_eq_small_const:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    lsl w8, w0, #2
+; CHECK-NEXT:    cmp w8, #124 // =124
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %yy = shl i32 %y, 2
+  %cmp = icmp eq i32 124, %yy
+  ret i1 %cmp
+}
+
+define i1 @shl_eq_big_const(i32 %y) nounwind {
+; CHECK-LABEL: shl_eq_big_const:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov w8, #24908
+; CHECK-NEXT:    movk w8, #188, lsl #16
+; CHECK-NEXT:    cmp w8, w0, lsl #2
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %yy = shl i32 %y, 2
+  %cmp = icmp eq i32 12345676, %yy
+  ret i1 %cmp
+}
+
+; FIXME: Fold this.
+define i1 @shl_eq_big_const_instcombine(i32 %y) #0 {
+; CHECK-LABEL: shl_eq_big_const_instcombine:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov w9, #6227
+; CHECK-NEXT:    and w8, w0, #0x3fffffff
+; CHECK-NEXT:    movk w9, #47, lsl #16
+; CHECK-NEXT:    cmp w8, w9
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %yy.mask = and i32 %y, 1073741823
+  %cmp = icmp eq i32 %yy.mask, 3086419
+  ret i1 %cmp
+}
+
+define i1 @lshr_eq(i32 %x, i32 %y) nounwind {
+; CHECK-LABEL: lshr_eq:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    cmp w0, w1, lsr #2
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %yy = lshr i32 %y, 2
+  %cmp = icmp eq i32 %x, %yy
+  ret i1 %cmp
+}
+
+define i1 @lshr_eq_2(i32 %x, i32 %y) nounwind {
+; CHECK-LABEL: lshr_eq_2:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    cmp w0, w1, lsr #2
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %yy = lshr i32 %y, 2
+  %cmp = icmp eq i32 %yy, %x
+  ret i1 %cmp
+}
+
+define i1 @and16_eq(i32 %x, i32 %y) nounwind {
+; CHECK-LABEL: and16_eq:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    cmp w0, w1, uxth
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %yy = and i32 %y, 65535
+  %cmp = icmp eq i32 %x, %yy
+  ret i1 %cmp
+}
+
+define i1 @and16_eq_2(i32 %x, i32 %y) nounwind {
+; CHECK-LABEL: and16_eq_2:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    cmp w0, w1, uxth
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %yy = and i32 %y, 65535
+  %cmp = icmp eq i32 %yy, %x
+  ret i1 %cmp
+}
+
+define i1 @and32_eq(i64 %x, i64 %y) nounwind {
+; CHECK-LABEL: and32_eq:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    cmp x0, w1, uxtw
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %yy = and i64 %y, 4294967295
+  %cmp = icmp eq i64 %x, %yy
+  ret i1 %cmp
+}
+
+define i1 @and32_eq_2(i64 %x, i64 %y) nounwind {
+; CHECK-LABEL: and32_eq_2:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    cmp x0, w1, uxtw
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %yy = and i64 %y, 4294967295
+  %cmp = icmp eq i64 %yy, %x
+  ret i1 %cmp
+}
+
+define i1 @shl_and32_eq(i64 %x, i64 %y) nounwind {
+; CHECK-LABEL: shl_and32_eq:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    cmp x0, w1, uxtw #2
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %y2 = and i64 %y, 4294967295
+  %yy = shl i64 %y2, 2
+  %cmp = icmp eq i64 %x, %yy
+  ret i1 %cmp
+}
+
+define i1 @shl_and32_eq_2(i64 %x, i64 %y) nounwind {
+; CHECK-LABEL: shl_and32_eq_2:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    cmp x0, w1, uxtw #2
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %y2 = and i64 %y, 4294967295
+  %yy = shl i64 %y2, 2
+  %cmp = icmp eq i64 %yy, %x
+  ret i1 %cmp
+}
+
+; FIXME: Fold this; it's equivalent to uxtw #2
+define i1 @shl_and32_eq_instcombine(i64 %x, i64 %y) {
+; CHECK-LABEL: shl_and32_eq_instcombine:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    ubfiz x8, x1, #2, #32
+; CHECK-NEXT:    cmp x8, x0
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %y2 = shl i64 %y, 2
+  %yy = and i64 %y2, 17179869180
+  %cmp = icmp eq i64 %yy, %x
+  ret i1 %cmp
+}
+
+; FIXME: Fold this; it's equivalent to uxtw #2
+define i1 @shl_and32_eq_instcombine_2(i64 %x, i64 %y) {
+; CHECK-LABEL: shl_and32_eq_instcombine_2:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    ubfiz x8, x1, #2, #32
+; CHECK-NEXT:    cmp x0, x8
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %y2 = shl i64 %y, 2
+  %yy = and i64 %y2, 17179869180
+  %cmp = icmp eq i64 %x, %yy
+  ret i1 %cmp
+}
+
+; FIXME: This is equivalent to sxtw #1
+define i1 @sext_shift_eq(i32 %x, i32 %y) nounwind {
+; CHECK-LABEL: sext_shift_eq:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    lsl w8, w1, #16
+; CHECK-NEXT:    cmp w0, w8, asr #15
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %y2 = shl i32 %y, 16
+  %yy = ashr i32 %y2, 15
+  %cmp = icmp eq i32 %x, %yy
+  ret i1 %cmp
+}
+
+define i1 @sext_shift_eq_2(i32 %x, i32 %y) nounwind {
+; CHECK-LABEL: sext_shift_eq_2:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    lsl w8, w1, #16
+; CHECK-NEXT:    cmp w0, w8, asr #15
+; CHECK-NEXT:    cset w0, eq
+; CHECK-NEXT:    ret
+  %y2 = shl i32 %y, 16
+  %yy = ashr i32 %y2, 15
+  %cmp = icmp eq i32 %yy, %x
+  ret i1 %cmp
+}
Index: test/CodeGen/AArch64/lack-of-signed-truncation-check.ll
===================================================================
--- test/CodeGen/AArch64/lack-of-signed-truncation-check.ll
+++ test/CodeGen/AArch64/lack-of-signed-truncation-check.ll
@@ -35,8 +35,7 @@
 define i1 @shifts_necmp_i32_i16(i32 %x) nounwind {
 ; CHECK-LABEL: shifts_necmp_i32_i16:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxth w8, w0
-; CHECK-NEXT:    cmp w8, w0
+; CHECK-NEXT:    cmp w0, w0, sxth
 ; CHECK-NEXT:    cset w0, ne
 ; CHECK-NEXT:    ret
   %tmp0 = shl i32 %x, 16 ; 32-16
@@ -48,8 +47,7 @@
 define i1 @shifts_necmp_i32_i8(i32 %x) nounwind {
 ; CHECK-LABEL: shifts_necmp_i32_i8:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxtb w8, w0
-; CHECK-NEXT:    cmp w8, w0
+; CHECK-NEXT:    cmp w0, w0, sxtb
 ; CHECK-NEXT:    cset w0, ne
 ; CHECK-NEXT:    ret
   %tmp0 = shl i32 %x, 24 ; 32-8
@@ -61,8 +59,7 @@
 define i1 @shifts_necmp_i64_i32(i64 %x) nounwind {
 ; CHECK-LABEL: shifts_necmp_i64_i32:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxtw x8, w0
-; CHECK-NEXT:    cmp x8, x0
+; CHECK-NEXT:    cmp x0, w0, sxtw
 ; CHECK-NEXT:    cset w0, ne
 ; CHECK-NEXT:    ret
   %tmp0 = shl i64 %x, 32 ; 64-32
@@ -74,8 +71,7 @@
 define i1 @shifts_necmp_i64_i16(i64 %x) nounwind {
 ; CHECK-LABEL: shifts_necmp_i64_i16:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxth x8, w0
-; CHECK-NEXT:    cmp x8, x0
+; CHECK-NEXT:    cmp x0, w0, sxth
 ; CHECK-NEXT:    cset w0, ne
 ; CHECK-NEXT:    ret
   %tmp0 = shl i64 %x, 48 ; 64-16
@@ -87,8 +83,7 @@
 define i1 @shifts_necmp_i64_i8(i64 %x) nounwind {
 ; CHECK-LABEL: shifts_necmp_i64_i8:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxtb x8, w0
-; CHECK-NEXT:    cmp x8, x0
+; CHECK-NEXT:    cmp x0, w0, sxtb
 ; CHECK-NEXT:    cset w0, ne
 ; CHECK-NEXT:    ret
   %tmp0 = shl i64 %x, 56 ; 64-8
@@ -196,8 +191,7 @@
 define i1 @add_ugecmp_i32_i16(i32 %x) nounwind {
 ; CHECK-LABEL: add_ugecmp_i32_i16:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxth w8, w0
-; CHECK-NEXT:    cmp w8, w0
+; CHECK-NEXT:    cmp w0, w0, sxth
 ; CHECK-NEXT:    cset w0, ne
 ; CHECK-NEXT:    ret
   %tmp0 = add i32 %x, 32768 ; 1U << (16-1)
@@ -208,8 +202,7 @@
 define i1 @add_ugecmp_i32_i8(i32 %x) nounwind {
 ; CHECK-LABEL: add_ugecmp_i32_i8:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxtb w8, w0
-; CHECK-NEXT:    cmp w8, w0
+; CHECK-NEXT:    cmp w0, w0, sxtb
 ; CHECK-NEXT:    cset w0, ne
 ; CHECK-NEXT:    ret
   %tmp0 = add i32 %x, 128 ; 1U << (8-1)
@@ -220,8 +213,7 @@
 define i1 @add_ugecmp_i64_i32(i64 %x) nounwind {
 ; CHECK-LABEL: add_ugecmp_i64_i32:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxtw x8, w0
-; CHECK-NEXT:    cmp x8, x0
+; CHECK-NEXT:    cmp x0, w0, sxtw
 ; CHECK-NEXT:    cset w0, ne
 ; CHECK-NEXT:    ret
   %tmp0 = add i64 %x, 2147483648 ; 1U << (32-1)
@@ -232,8 +224,7 @@
 define i1 @add_ugecmp_i64_i16(i64 %x) nounwind {
 ; CHECK-LABEL: add_ugecmp_i64_i16:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxth x8, w0
-; CHECK-NEXT:    cmp x8, x0
+; CHECK-NEXT:    cmp x0, w0, sxth
 ; CHECK-NEXT:    cset w0, ne
 ; CHECK-NEXT:    ret
   %tmp0 = add i64 %x, 32768 ; 1U << (16-1)
@@ -244,8 +235,7 @@
 define i1 @add_ugecmp_i64_i8(i64 %x) nounwind {
 ; CHECK-LABEL: add_ugecmp_i64_i8:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxtb x8, w0
-; CHECK-NEXT:    cmp x8, x0
+; CHECK-NEXT:    cmp x0, w0, sxtb
 ; CHECK-NEXT:    cset w0, ne
 ; CHECK-NEXT:    ret
   %tmp0 = add i64 %x, 128 ; 1U << (8-1)
Index: test/CodeGen/AArch64/signed-truncation-check.ll
===================================================================
--- test/CodeGen/AArch64/signed-truncation-check.ll
+++ test/CodeGen/AArch64/signed-truncation-check.ll
@@ -35,8 +35,7 @@
 define i1 @shifts_eqcmp_i32_i16(i32 %x) nounwind {
 ; CHECK-LABEL: shifts_eqcmp_i32_i16:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxth w8, w0
-; CHECK-NEXT:    cmp w8, w0
+; CHECK-NEXT:    cmp w0, w0, sxth
 ; CHECK-NEXT:    cset w0, eq
 ; CHECK-NEXT:    ret
   %tmp0 = shl i32 %x, 16 ; 32-16
@@ -48,8 +47,7 @@
 define i1 @shifts_eqcmp_i32_i8(i32 %x) nounwind {
 ; CHECK-LABEL: shifts_eqcmp_i32_i8:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxtb w8, w0
-; CHECK-NEXT:    cmp w8, w0
+; CHECK-NEXT:    cmp w0, w0, sxtb
 ; CHECK-NEXT:    cset w0, eq
 ; CHECK-NEXT:    ret
   %tmp0 = shl i32 %x, 24 ; 32-8
@@ -61,8 +59,7 @@
 define i1 @shifts_eqcmp_i64_i32(i64 %x) nounwind {
 ; CHECK-LABEL: shifts_eqcmp_i64_i32:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxtw x8, w0
-; CHECK-NEXT:    cmp x8, x0
+; CHECK-NEXT:    cmp x0, w0, sxtw
 ; CHECK-NEXT:    cset w0, eq
 ; CHECK-NEXT:    ret
   %tmp0 = shl i64 %x, 32 ; 64-32
@@ -74,8 +71,7 @@
 define i1 @shifts_eqcmp_i64_i16(i64 %x) nounwind {
 ; CHECK-LABEL: shifts_eqcmp_i64_i16:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxth x8, w0
-; CHECK-NEXT:    cmp x8, x0
+; CHECK-NEXT:    cmp x0, w0, sxth
 ; CHECK-NEXT:    cset w0, eq
 ; CHECK-NEXT:    ret
   %tmp0 = shl i64 %x, 48 ; 64-16
@@ -87,8 +83,7 @@
 define i1 @shifts_eqcmp_i64_i8(i64 %x) nounwind {
 ; CHECK-LABEL: shifts_eqcmp_i64_i8:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxtb x8, w0
-; CHECK-NEXT:    cmp x8, x0
+; CHECK-NEXT:    cmp x0, w0, sxtb
 ; CHECK-NEXT:    cset w0, eq
 ; CHECK-NEXT:    ret
   %tmp0 = shl i64 %x, 56 ; 64-8
@@ -198,8 +193,7 @@
 define i1 @add_ultcmp_i32_i16(i32 %x) nounwind {
 ; CHECK-LABEL: add_ultcmp_i32_i16:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxth w8, w0
-; CHECK-NEXT:    cmp w8, w0
+; CHECK-NEXT:    cmp w0, w0, sxth
 ; CHECK-NEXT:    cset w0, eq
 ; CHECK-NEXT:    ret
   %tmp0 = add i32 %x, 32768 ; 1U << (16-1)
@@ -210,8 +204,7 @@
 define i1 @add_ultcmp_i32_i8(i32 %x) nounwind {
 ; CHECK-LABEL: add_ultcmp_i32_i8:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxtb w8, w0
-; CHECK-NEXT:    cmp w8, w0
+; CHECK-NEXT:    cmp w0, w0, sxtb
 ; CHECK-NEXT:    cset w0, eq
 ; CHECK-NEXT:    ret
   %tmp0 = add i32 %x, 128 ; 1U << (8-1)
@@ -222,8 +215,7 @@
 define i1 @add_ultcmp_i64_i32(i64 %x) nounwind {
 ; CHECK-LABEL: add_ultcmp_i64_i32:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxtw x8, w0
-; CHECK-NEXT:    cmp x8, x0
+; CHECK-NEXT:    cmp x0, w0, sxtw
 ; CHECK-NEXT:    cset w0, eq
 ; CHECK-NEXT:    ret
   %tmp0 = add i64 %x, 2147483648 ; 1U << (32-1)
@@ -234,8 +226,7 @@
 define i1 @add_ultcmp_i64_i16(i64 %x) nounwind {
 ; CHECK-LABEL: add_ultcmp_i64_i16:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxth x8, w0
-; CHECK-NEXT:    cmp x8, x0
+; CHECK-NEXT:    cmp x0, w0, sxth
 ; CHECK-NEXT:    cset w0, eq
 ; CHECK-NEXT:    ret
   %tmp0 = add i64 %x, 32768 ; 1U << (16-1)
@@ -246,8 +237,7 @@
 define i1 @add_ultcmp_i64_i8(i64 %x) nounwind {
 ; CHECK-LABEL: add_ultcmp_i64_i8:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    sxtb x8, w0
-; CHECK-NEXT:    cmp x8, x0
+; CHECK-NEXT:    cmp x0, w0, sxtb
 ; CHECK-NEXT:    cset w0, eq
 ; CHECK-NEXT:    ret
   %tmp0 = add i64 %x, 128 ; 1U << (8-1)