src/cmd/compile/internal/ssa/rewrite.go      | 2 +-
 src/cmd/compile/internal/ssa/rewrite_test.go | 1 +

diff --git a/src/cmd/compile/internal/ssa/rewrite.go b/src/cmd/compile/internal/ssa/rewrite.go
index f5d1a7889fb19f6fb4bdbe64f1df4d337bf2f079..9e5ef68b1e9551664405154f268561aa2343ae37 100644
--- a/src/cmd/compile/internal/ssa/rewrite.go
+++ b/src/cmd/compile/internal/ssa/rewrite.go
@@ -1469,7 +1469,7 @@ 	mask := mergePPC64RShiftMask(m, s, 32)
 	if !isPPC64WordRotateMask(mask) {
 		return 0
 	}
-	return encodePPC64RotateMask(32-s, mask, 32)
+	return encodePPC64RotateMask((32-s)&31, mask, 32)
 }
 
 // Test if a shift right feeding into a CLRLSLDI can be merged into RLWINM.
diff --git a/src/cmd/compile/internal/ssa/rewrite_test.go b/src/cmd/compile/internal/ssa/rewrite_test.go
index 6fe429e85a67f3c509f1cdc5dafdbfdb55027882..64d128b8a4d7cd36e1a0ce93412b85b89fe43f5d 100644
--- a/src/cmd/compile/internal/ssa/rewrite_test.go
+++ b/src/cmd/compile/internal/ssa/rewrite_test.go
@@ -205,6 +205,7 @@ 		{0x0F0000FF, 4, false, 0, 0},
 		{0x00000000, 4, false, 0, 0},
 		{0xF0000000, 4, false, 0, 0},
 		{0xF0000000, 32, false, 0, 0},
+		{0xFFFFFFFF, 0, true, 0, 0xFFFFFFFF},
 	}
 	for i, v := range tests {
 		result := mergePPC64AndSrwi(v.and, v.srw)