[PATCH v2 46/69] target/arm: Handle FPCR.AH in vector FCMLA

[Peter Maydell]

From: Richard Henderson <richard.henderson@linaro.org>

The negation step in FCMLA mustn't negate a NaN when FPCR.AH
is set. Handle this by passing FPCR.AH to the helper via the
SIMD data field, and use this to select whether to do the
negation via XOR or via the muladd negate_product flag.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20250129013857.135256-26-richard.henderson@linaro.org
[PMM: Expanded commit message]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/tcg/translate-a64.c |  2 +-
 target/arm/tcg/vec_helper.c    | 66 ++++++++++++++++++++--------------
 2 files changed, 40 insertions(+), 28 deletions(-)

diff --git a/target/arm/tcg/translate-a64.c b/target/arm/tcg/translate-a64.c
index c209ac84228..c45a9822281 100644
--- a/target/arm/tcg/translate-a64.c
+++ b/target/arm/tcg/translate-a64.c
@@ -6175,7 +6175,7 @@ static bool trans_FCMLA_v(DisasContext *s, arg_FCMLA_v *a)
 
     gen_gvec_op4_fpst(s, a->q, a->rd, a->rn, a->rm, a->rd,
                       a->esz == MO_16 ? FPST_A64_F16 : FPST_A64,
-                      a->rot, fn[a->esz]);
+                      a->rot | (s->fpcr_ah << 2), fn[a->esz]);
     return true;
 }
 
diff --git a/target/arm/tcg/vec_helper.c b/target/arm/tcg/vec_helper.c
index fc3e6587b81..630513f00b2 100644
--- a/target/arm/tcg/vec_helper.c
+++ b/target/arm/tcg/vec_helper.c
@@ -965,22 +965,26 @@ void HELPER(gvec_fcmlah)(void *vd, void *vn, void *vm, 
void *va,
     uintptr_t opr_sz = simd_oprsz(desc);
     float16 *d = vd, *n = vn, *m = vm, *a = va;
     intptr_t flip = extract32(desc, SIMD_DATA_SHIFT, 1);
-    uint32_t neg_imag = extract32(desc, SIMD_DATA_SHIFT + 1, 1);
-    uint32_t neg_real = flip ^ neg_imag;
+    uint32_t fpcr_ah = extract32(desc, SIMD_DATA_SHIFT + 2, 1);
+    uint32_t negf_imag = extract32(desc, SIMD_DATA_SHIFT + 1, 1);
+    uint32_t negf_real = flip ^ negf_imag;
+    float16 negx_imag, negx_real;
     uintptr_t i;
 
-    /* Shift boolean to the sign bit so we can xor to negate.  */
-    neg_real <<= 15;
-    neg_imag <<= 15;
+    /* With AH=0, use negx; with AH=1 use negf. */
+    negx_real = (negf_real & ~fpcr_ah) << 15;
+    negx_imag = (negf_imag & ~fpcr_ah) << 15;
+    negf_real = (negf_real & fpcr_ah ? float_muladd_negate_product : 0);
+    negf_imag = (negf_imag & fpcr_ah ? float_muladd_negate_product : 0);
 
     for (i = 0; i < opr_sz / 2; i += 2) {
         float16 e2 = n[H2(i + flip)];
-        float16 e1 = m[H2(i + flip)] ^ neg_real;
+        float16 e1 = m[H2(i + flip)] ^ negx_real;
         float16 e4 = e2;
-        float16 e3 = m[H2(i + 1 - flip)] ^ neg_imag;
+        float16 e3 = m[H2(i + 1 - flip)] ^ negx_imag;
 
-        d[H2(i)] = float16_muladd(e2, e1, a[H2(i)], 0, fpst);
-        d[H2(i + 1)] = float16_muladd(e4, e3, a[H2(i + 1)], 0, fpst);
+        d[H2(i)] = float16_muladd(e2, e1, a[H2(i)], negf_real, fpst);
+        d[H2(i + 1)] = float16_muladd(e4, e3, a[H2(i + 1)], negf_imag, fpst);
     }
     clear_tail(d, opr_sz, simd_maxsz(desc));
 }
@@ -1025,22 +1029,26 @@ void HELPER(gvec_fcmlas)(void *vd, void *vn, void *vm, 
void *va,
     uintptr_t opr_sz = simd_oprsz(desc);
     float32 *d = vd, *n = vn, *m = vm, *a = va;
     intptr_t flip = extract32(desc, SIMD_DATA_SHIFT, 1);
-    uint32_t neg_imag = extract32(desc, SIMD_DATA_SHIFT + 1, 1);
-    uint32_t neg_real = flip ^ neg_imag;
+    uint32_t fpcr_ah = extract32(desc, SIMD_DATA_SHIFT + 2, 1);
+    uint32_t negf_imag = extract32(desc, SIMD_DATA_SHIFT + 1, 1);
+    uint32_t negf_real = flip ^ negf_imag;
+    float32 negx_imag, negx_real;
     uintptr_t i;
 
-    /* Shift boolean to the sign bit so we can xor to negate.  */
-    neg_real <<= 31;
-    neg_imag <<= 31;
+    /* With AH=0, use negx; with AH=1 use negf. */
+    negx_real = (negf_real & ~fpcr_ah) << 31;
+    negx_imag = (negf_imag & ~fpcr_ah) << 31;
+    negf_real = (negf_real & fpcr_ah ? float_muladd_negate_product : 0);
+    negf_imag = (negf_imag & fpcr_ah ? float_muladd_negate_product : 0);
 
     for (i = 0; i < opr_sz / 4; i += 2) {
         float32 e2 = n[H4(i + flip)];
-        float32 e1 = m[H4(i + flip)] ^ neg_real;
+        float32 e1 = m[H4(i + flip)] ^ negx_real;
         float32 e4 = e2;
-        float32 e3 = m[H4(i + 1 - flip)] ^ neg_imag;
+        float32 e3 = m[H4(i + 1 - flip)] ^ negx_imag;
 
-        d[H4(i)] = float32_muladd(e2, e1, a[H4(i)], 0, fpst);
-        d[H4(i + 1)] = float32_muladd(e4, e3, a[H4(i + 1)], 0, fpst);
+        d[H4(i)] = float32_muladd(e2, e1, a[H4(i)], negf_real, fpst);
+        d[H4(i + 1)] = float32_muladd(e4, e3, a[H4(i + 1)], negf_imag, fpst);
     }
     clear_tail(d, opr_sz, simd_maxsz(desc));
 }
@@ -1085,22 +1093,26 @@ void HELPER(gvec_fcmlad)(void *vd, void *vn, void *vm, 
void *va,
     uintptr_t opr_sz = simd_oprsz(desc);
     float64 *d = vd, *n = vn, *m = vm, *a = va;
     intptr_t flip = extract32(desc, SIMD_DATA_SHIFT, 1);
-    uint64_t neg_imag = extract32(desc, SIMD_DATA_SHIFT + 1, 1);
-    uint64_t neg_real = flip ^ neg_imag;
+    uint32_t fpcr_ah = extract32(desc, SIMD_DATA_SHIFT + 2, 1);
+    uint32_t negf_imag = extract32(desc, SIMD_DATA_SHIFT + 1, 1);
+    uint32_t negf_real = flip ^ negf_imag;
+    float64 negx_real, negx_imag;
     uintptr_t i;
 
-    /* Shift boolean to the sign bit so we can xor to negate.  */
-    neg_real <<= 63;
-    neg_imag <<= 63;
+    /* With AH=0, use negx; with AH=1 use negf. */
+    negx_real = (uint64_t)(negf_real & ~fpcr_ah) << 63;
+    negx_imag = (uint64_t)(negf_imag & ~fpcr_ah) << 63;
+    negf_real = (negf_real & fpcr_ah ? float_muladd_negate_product : 0);
+    negf_imag = (negf_imag & fpcr_ah ? float_muladd_negate_product : 0);
 
     for (i = 0; i < opr_sz / 8; i += 2) {
         float64 e2 = n[i + flip];
-        float64 e1 = m[i + flip] ^ neg_real;
+        float64 e1 = m[i + flip] ^ negx_real;
         float64 e4 = e2;
-        float64 e3 = m[i + 1 - flip] ^ neg_imag;
+        float64 e3 = m[i + 1 - flip] ^ negx_imag;
 
-        d[i] = float64_muladd(e2, e1, a[i], 0, fpst);
-        d[i + 1] = float64_muladd(e4, e3, a[i + 1], 0, fpst);
+        d[i] = float64_muladd(e2, e1, a[i], negf_real, fpst);
+        d[i + 1] = float64_muladd(e4, e3, a[i + 1], negf_imag, fpst);
     }
     clear_tail(d, opr_sz, simd_maxsz(desc));
 }
-- 
2.34.1